IB Thermal Concepts

A tutorial sheet of harder questions on sub-topic 3.1 thermal concepts is given below.

specific heat capacity of ice = 2200 J/Kg/°C, specific latent heat of fusion of ice=334000 J/kg, specific heat capacity of water=4200J/kg/°C.

1. 25.0 g of ice is at a temperature of -10 °C.The ice is placed in 300 g of water at 20°C. What is the temperature when thermal equilibrium is reached? [11.9°C]
2. 300.0 g of ice at 0°C is placed in 100.0 g of water at 15°C. What fraction of the ice melts?
3. 500.0 g of ice at 0°C is placed in water at 20°C. What is the mass of the water if one half of the ice melts?

IB Physics Capacitors

A tutorial sheet of capacitor questions starts below

1. The distance between the parallel plates of a capacitor with an air gap is doubled, the potential difference between the plates remaining constant. Does the electric field strength between the plates change?
2. The distance between the parallel plates of a capacitor with an air gap is doubled, the charge on each plate remaining constant. Does the electric field strength between the plates change?
3. Does the capacitance increase, decrease or stay the same when a slab of dielectric material is placed between the plates which are connected to a battery of constant voltage?
4. Does the capacitance increase, decrease or stay the same when a slab of dielectric material is placed between the plates on which the charge is kept constant?
5. Why does the presence of a dielectric material between the plates change the capacitance?
6. Does the force between the plates of a parallel plate capacitor increse, decrease or stay the same when a parallel sided dielectric slab half fills the distance between the plates, the plates being connected to a battery of constant voltage? When is the total energy of the capacitor greatest, before or after the slab is inserted? Explain the difference.
7. A parallel plate capacitor is charged and then isolated from the supply. The plates are then moved further apart. State the changes that occur in the potential difference between the plates, the energy stored in the capacitor, the electric field strength between the plates and the capacitance.[increases,increases,constant,decreases]
8. A parallel plate capacitor is maintained at a constant voltage. The plates are then moved further apart. State the changes that occur in the charge stored on the plates, the energy stored by the capacitor, the electric field strength between the plates and the capacitance.[decreases, decreases, decreases, decreases]

HSC Physics Interference of Waves

A tutorial sheet on double slit interference is given below.

1. Coherent, monochromatic light passes through a single narrow rectangular slit. Describe the intensity pattern that forms on a screen at a large distance from the slit.
2. Coherent, monochromatic light passes through two parallel narrow rectangular slits. Describe the intensity pattern that forms on a screen at a large distance from the slits.
3. Coherent red light of wavelength 650 nm passes through a double slit of separation 0.2 mm. Determine the distance between successive bright fringes on a screen 3.0 m from the double slit.
4. What is the path difference when the first order maximum forms on a screen?
5. In a double slit experiment one of the slits is covered up. Is the central maximum brighter when one of the slits is covered?
6. Microwaves have a wavelength of 3.0 cm. A micowave detector is placed alongside the microwave source. The microwaves are aimed perpendicular at thin parallel perspex and metal sheets. Some microwaves reflect back from the perspex and all are reflected back by the metal sheet. What is the least distance between the sheets when constructive interference occurs in the reflected microwaves?

HSC Physics Polarisation

A tutorial sheet of polarisation problems is given below

1. When is a beam of light polarised?
2. A beam of unpolarised light of intensity 4000 Wm^-2 strikes a polarising filter. What is the transmitted intensity?
3. Unpolarised light of intensity I passes through three polarising filters placed in a line. The polarising directions of the filters are are inclined at 45° to each other. Determine the intensity transmitted by the third filter.
4. Polarised light of intensity I passes through three polarising filters placed in a line. The angle between the plane of polaristion of the light and the polarising direction of the first filter is 45°. If the polarising directions of the filters are inclined at 45° to each other, determine the intensity transmitted by the third filter.
5. Light is polarised with its electric field in the horizontal plane. The light strikes two polarising filters, one behind the other. The first filter has its polaring direction at 25° to the horizontal and the second at 50° to the horizontal. What percentage of the intensity of the original light passes through the second filter?

HSC Physics Electric Field Lines

Electric field patterns are commonly drawn incorrectly. A tutorial sheet of field line questions is given below.

1. Equal point charges +Q and +Q are placed a distance 2d apart in a vacuum. Draw the electric field pattern around these charges. Do the electric field lines approach the perpendicular bisector to the line joining the charges? [see the cover of W J Duffin Electricity and Magnetism]
2. Point charges +4Q and -Q are placed a distance d apart in a vacuum. Draw the electric field lines around these charges.
3. Draw the electric field lines of an electric dipole when it is seen close up.
4. Draw the electric field lines of an electric dipole when it is measured from a large distance (a distance much greater than the charge separation). Is the field zero at a large distance?
5. Point charges -Q, +2Q and -Q are placed in a straight line in a vacuum. The end charges are each a distance d from the middle charge. Draw the electric field lines around this combination.
6. A long metal cylinder of inner and outer radii a and b respectively carries a total charge +Q. Draw the electric field lines of this arrangement.
7. A long metal cylinder of inner and outer radii a and b respectively is uncharged. The cylinder is placed in a uniform electric field that is perpendicular to the axis of the cylinder. Draw the electric field lines of this combination. What is the electric field strength inside the cylinder?

HSC Physics Electricity and Magnetism

In the Electricity and Magnetism section of the HSC Physics Formuae Sheet the equations involving an angle 𝜽 do not all have the angle measured in the same way. A tutorial set of substitution questions is given below.

1. A charge of +2.0 μC has a velocity of 3.0×10⁷ ms^-1 to the right of the page. The particle is in a uniform magnetic field of 1.0 mT acting out of the page. Determine the magnetic force acting on the charge.
2. A coil of area 10 cm² has its plane at an angle of 30° to a uniform magnetic field of 100 mT. What is the magnetic flux through the coil?
3. A coil of cross sectional area 30 mm² containing 100 turns carries a current of 20 mA. The axis of the coil makes an angle of 20° with a uniform magnetic field of 2.0x10^-2 T. Determine the size of the torque acting on the current.
4. A straight wire of length 52 cm carries a current of 300 μA in a uniform magnetic field of 350 mT. If the wire makes an angle of 123° with the magnetic field lines, find the size of the magnetic force acting on the current.
5. The Earth's magnetic field vector at Sydney is 57 μT N12°36'E at 64°19' below the horizontal. At a certain instant an electron is moving in this magnetic field towards the east at a speed of 3.0x10⁷ ms^-1. Determine (a) the magnitude of the magnetic force acting on the electron at this instant (b) the direction of the magnetic force acting at this instant, and (c) the period of the motion of the electron in the uniform magnetic field.

IB Physics Static and Kinetic Friction

A tutorial sheet on static and kinetic friction problems from subtopic 2.2 forces is given below

1. A 3.0 kg block is at rest at rest on each of two rough inclined planes. One incline makes an angle of 37° with the horizontal, the other 53°. On which block is a greater force of static friction acting?
2. A block of mass 2.0 kg is on a rough horizontal table. The coefficient of static friction between the block and the table is 0.4. A horizontal force of 5.0 N to the right is applied to the block. What is the force of static friction between the block and the table?
3. A block of wood of mass 4.0 kg has a brick of mass 2.0 kg sitting on it. The block rests on a smooth horizontal surface and the block and brick are initially at rest. A constant horizontal force of 12.0 N is applied to the block. What are the speeds of the block and the brick after 12.0 s? Assume that the brick stays on the block and that the coefficients of static friction and kinetic friction between the surfaces are 0.2 and 0.1 respectively.

IB Physics Equations of Motion

Below is a tutorial sheet of harder problems on subtopic 2.1

1. A ball falls from rest near the surface of the Earth. The ball falls 1.0 m in the last second of its fall. From what vertical height was the ball released? Neglect air resistance.
2. A stone is released from rest at a height of 200.0 m above the surface of the Earth. At the same instant a ball is projected vertically upwards from the ground from directly below the stone. If they meet after 4.0 s at what speed was the ball projected? Neglect air resistance.
3. A ball is projected vertically upwards from the surface of the Earth. The ball is above a height of 125.0 m for a total time of 3.0 s. At what speed was the ball projected? Neglect air resistance.
4. A car of length L moves at a constant velocity u to the east. A truck of length T moves at a constant velocity v to the east. What is the time taken by the car to overtake the truck?
5. A car of length L moves with a constant acceleration a to the east. A truck of length T moves at a constant velocity v to the east. When the velocity of the car is u it starts to overtake the truck. What is the time taken to overtake the truck?
6. A particle moves with a constant acceleration a. If its maximum speed is v what is the least time to travel a distance d if it starts from rest?
7. A particle is initially at rest. Its acceleration increases uniformly from zero to a in a time interval t. What is the distance travelled in this time interval? [at²/6]

IB Physics Vectors

Below is a tutorial sheet on sub topic 1.3 vectors.

1. What is the component of a force of 5.0 N in a direction at 30° to itself?
2. What is the component of a force of 4.0 N in a direction at 90° to itself?
3. An object of weight W is held at rest on a smooth inclined plane of angle of elevation 𝜽 by a horizontal force H. What is the value of H?
4. An object of weight W is held at rest on a rough inclined plane of angle of elevation 𝜽 by a horizontal force H. If the coefficient of static friction is μ, determine the possible values of H.
5. Two light inextensible strings are tied to an object of weight W at the same point. The strings make angles of 30° and 60° with the vertical. Determine the tension in each string.
6. Three light strings of equal length are tied to the same point on an object of weight W. The other ends of the strings are tied to hooks on the ceiling, the strings forming the sides of a regular tetrahedron. What is the tension in each string?

IB Physics Uncertainties

A tutorial sheet on sub topic 1.2 is given below.

1. The mass of a pencil is measured once. The value is 4g. What is the uncertainty in this measurement?
2. A ball is released from rest and the time to fall a fixed distance is measured. The times are 0.5s, 0.5s, 0.6s and 0.6s. What is the uncertainty in the time of fall?
3. A student measures the following value for g in ms^-2: 9.81, 9.79, 9.84, 9.81, 9.75, 9.79, 9.83. Give the scientific value of g including its uncertainty. [9.80 ± 0.01 ms^-2]
4. A toy car moves in a straight line along a horizontal laboratory bench. The time taken to move a distance of 350cm is measured 5 times. The values are 6.2s, 6.5s, 6.4s, 6.3s and 6.0s. What is the average speed of the car?
5. In the previous question the distance is measured 5 times. The values are 340cm, 360cm, 345cm, 365cm, 355 cm. Using the previous time values, what is the average speed of the car?
6. The mass of a marble is measured five times. The values are 52g, 51g, 52g, 53g, 52g. The diameter is measured five times. The values are 35mm, 33mm, 36mm, 34mm and 35mm. Determine the density of the marble.
7. A uniform rod can oscillate freely about a horizontal axis through its end point. The time of small oscillations about its equilibrium position is given by T = 2𝜋√[I/(mgh)], where m is the mass of the rod, g the acceleration due to gravity, h the distance from the point of support to the centre of the rod and I is the moment of inertia of the rod about its point of support. The following data sets are obtained for the measurement of m, h and I respectively; {210g, 208g, 209g, 211g, 212g}, {0.50m, 0.49m, 0.51m, 0.48m, 0.49m}, {0.42kgm², 0.40kgm², 0.46kgm², 0.50kgm², 0.50kgm²}. Determine g from this data.
8. The radius of a circle is 14.6±0.5cm. Determine the area of the circle to the correct number of significant figures. [(6.70±0.46)×10² cm²]
9. What is the circumference of the circle in the previous question? [91.7±3.1cm]
10. If R=1800±36Ω and I=2.1±0.1mA, what is the value of RI? [3.8±0.3V]

IB Physics SpaceTime Diagram

A tutorial sheet of true-false questions on the spacetime diagram is given below.

ɣ=1/√(1-v²/c²)

1. Albert Einstein was not the first person to use a spacetime diagram.
2. The path of a particle in the (x,ct) plane on a spacetime diagram is called its world line.
3. A rigid rod is at rest in the S frame. At t=0 the spacetime coordinates of the ends of the rod in S are A=(0,0) and B=(L₀,0). The worldlines of A and B have the equations x=0 and x=L₀ respectively.
4. In question 3 take ɣ = 5/4 and L₀ as 2. Using a spacetime diagram the coordinates of A in S' when ct' = 4 are (-2.5,4) and the coordinates of B are (-0.83,4), the length of the rod in S' being 1.7 approximately.
5. A rigid rod is at rest in the S' frame. At t'=0 the spacetime coordinates of the ends of the rod in S' are P=(0,0) and Q=(L₀,0). The worldlines of P and Q have the equations x=0 and x=L₀ respectively.

IB Physics Relativity

A tutorial sheet of true-false questions on relativity is given below.

1. The speed of light (according to the local observer) near a black hole is 3.0x10⁸ m/s. A distant observer considers the speed of light to be much less than this.
2. The speed of light changes (according to a distant observer) as it passes through a gravitational field.
3. The speed of light is the same for all observers in a flat space.
4. Space can expand at a rate greater than c.
5. Nothing can escape from inside a black hole.
6. Particles can escape from the event horizon of a black hole.
7. Light leaving the horizon of a black hole undergoes a gravitational red shift and has an infinite wavelength at infinity and so cannot be detected.
8. The time coordinate of an event is the same value at all locations in the same inertial reference frame.
9. If an event occurs at x' at time t' in the inertial reference frame S' the event occurs at time ɣ(t' + v x'/c²) in another inertial frame S.
10. The proper time interval is the least time interval between two events as reckoned from any inertial reference frame.
11. The proper time interval is the time interval between two events in the inertial reference frame where the events occur at the same position.
12. The proper length of a rod is the length of the rod in the inertial reference frame where the rod is at rest.
13. The rest reference frame for a moving object is the reference frame in which the object is at rest.
14. On a spacetime diagram the units on each axis have the same scale.
15. On a spacetime diagram the worldline of a particle of non-zero rest mass cannot have a gradient less than 1.

IB HSC Thermal Physics

A tutorial sheet of true-false questions on thermal physics concepts is given below.

1. Particles of an ideal gas do not collide with each other.
2. Particles of an ideal gas all have the same speed.
3. The ideal gas approximation works best at high temperatures and pressures.
4. The pressure exerted by a gas is due to the momentum of the particles.
5. No heat energy flows between two objects at the same temperature.
6. A large mass at a low temperature has the same amount of heat energy as a smaller mass at a higher temperature.
7. To find the Kelvin temperature we add 273.16 to the celsius temperature.
8. An object of higher specific heat capacity takes a longer time interval to undergo a given temperature change than one of lower specific heat capacity.
9. Heat energy is the amount of energy a substance possesses.
10. The SI unit for thermal conductivity is the Jm^-2s^-1K^-1
11. A flat sheet of iron of mass m is left in the Sun and its temperature changes by T. If a flat sheet of iron of mass 2m is left in the Sun for the same time interval its temperature change is T/2.

IB HSC Physics Coulomb's Law

A tutorial sheet of harder problems on Coulomb’s law is given below.

1. Point charges +4Q and -Q are placed a distance d apart in a vacuum. Where is the resultant electric field zero?
2. Draw the electric field lines around the charges in question 1.
3. Two point charges +4Q and +Q are placed a distance d apart in a vacuum. Where is the resultant electric field zero?
4. Draw the electric field lines around the charges in question 3.
5. Three equal point charges +Q are placed at the vertices of an equilateral triangle of side d. Is the resultant electric field ever zero?
6. Draw the electric field lines around the charges in question 5.
7. Four equal point charges +Q are placed at the corners of a square of side d. Is the resultant electric field ever zero?
8. Draw the electric field lines around the charges in question 7.
9. Four equal point charges +Q are placed at the corners of a regular tetrahedron of side d. Calculate the magnitude of the resultant force acting on one of the charges. [F√6, where F is the force between two of the charges]
10. Eight equal point charges +Q are placed at the corners of a cube of side d. Is the resultant electric field zero at the centre of the cube?
11. *In question 10 what is the magnitude of the resulant electric field at a small distance from the centre of the cube?

HSC Physics Projectiles

A tutorial sheet of harder questions on projectiles is given below. Unless otherwise indicated, neglect air resistance and take g = 9.8 ms ^-2 .

1. A ball is thrown at 65 m/s at 32° to the horizontal. At what height does it strike a vertical wall 53 m from the point of projection? [28.6m]
2. A stone is projected at 24 m/s and strikes a wall 37 m from the point of projection at a height of 15 m above the level of projection. What are the angles of projection to the horizontal? [47.8°,64.3°]
3. A stone is thrown at 47 m/s at 35° above the horizontal from the edge of a cliff. The stone strikes the sea at an angle of 14° below the horizontal. What is the height of the cliff? [32.4m]
4. A projectile is thrown at 13° below the horizontal from the edge of a cliff. It hits the sea at 135 m/s at an angle of 23° below the horizontal. What is the speed of projection? [127.5m/s]
5. A projectile is thrown from a cliff and strikes the sea 56 m from the foot of the cliff at 97 m/s at 49° below the horizontal. What is the speed of projection? [90.7m/s]
6. If a projectile strikes the sea at 140 m/s at 35° below the horizontal after being in flight for 12.0 s, what is the angle at which it was projected? [+18.0°]
7. A projectile strikes the sea 65.0 m from the base of a cliff of height 127 m after being projected at 92.0 m/s. What is the angle of projection to the horizontal? [-60.9°]
8. When a projectile lands below its initial level the maximum horizontal range is obtained at an angle of projection less than 45°. In shotput the shot leaves the hand at a height h above the ground at a speed u. Show that the angle of projection above the horizontal for maximum range is given by tan𝜽=1/(√(1+2gh/v²)).
9. A projectile is thrown at an angle of 45° to the horizontal. Sketch, on the same axes, the path of the projectile when (i) air resistance is neglected, (ii) air resistance is included.
10. A horizontal tunnel has a height of 3.00 m. A ball is thrown inside the tunnel with an initial speed of 18.0 m/s. What is the greatest horizontal distance the ball can travel before it bounces for the first time?[25.5m]

IB Physics Electric and Magnetic Fields

A tutorial sheet on electric and magnetic fields follows.

1. A charge +Q is at rest in the laboratory. Show the electric field around the charge in the laboratory reference frame.
2. A charge +Q moves to the right at a constant velocity v relative to the laboratory. Draw the electric field of the charge (i) in the reference frame of the charge, (ii) in the laboratory reference frame.
3. Two charges, +Q and +Q, both move to the right at a constant velocity v relative to the laboratory on parallel paths. In the reference frame of the charges, the line joining the charges is perpendicular to the velocity of the charges and has length d. Determine the magnitude of the force between the charges in (i) the reference frame of the charges, (ii) the laboratory reference frame.
4. A current I flows in the same direction in each of two long parallel wires. Determine the force between the wires in (i) the laboratory reference frame, (ii) a refernce frame moving parallel to the wires at the speed of the charges.
5. An electric field exists in the laboratory reference frame S. A reference frame S' moves at a constant velocity relative to the laboratory frame. (i) is an electric field present in s' ? (ii) is a magnetic field present in S' ?
6. A magnetic field exists in the laboratory reference frame S. A reference frame S' moves at a constant velocity relative to the laboratory frame. (i) is an electric field present in S' ? (ii) is a magnetic field present in S' ?

HSC Physics Exam 2018

Here are some final study notes for the HSC Physics examination on Thursday 1st November 2018. This list will be updated during the time up to the exam.

Space

1. Weight and gravitational force are the same.
2. Work done is the change in gravitational potential energy.
3. Work done is the area under the gravitational force versus distance graph.
4. Gravitational force is the negative gradient of the gravitational potential energy versus distance graph.
5. "g-force" is not a force. The net force that accelerates an astronaut upwards is the force of the seat pushing upwards minus the weight of the astronaut pulling downwards. g-force is the ratio of the seat force to the weight force.
6. A train is moving to the east and slowing down with deceleration g. A person in the train drops a ball. Relative to the person in the train the ball moves with a vertical acceleration component g and a horizontal acceleration component g and appears to fall forward in a straight line at 45° below the horizontal.
7. The escape speed from a point in a gravitational field is the speed with which a mass is projected so that its total energy is zero.
8. An object is said to be weightless when it is in a reference frame that is moving at the acceleration due to gravity.
9. Time dilation is when the time interval measured on a moving clock is less than the time interval measured on a clock at rest.

Motors and Generators

1. The torque on a coil carrying a current is maximum when it is parallel to the magnetic field.
2. The torque acting on one side of a square coil carrying a current in a magnetic field is one half of the total torque acting on the coil.
3. When a conductor moves relative to a uniform magnetic field an emf is induced in the conductor. If the emf allows a current to flow a force opposing the change is exerted by the magnetic field on the current.
4. When a conductor moves relative to a uniform electric field no emf is induced in the conductor.
5. In induction effects, the external magnetic field exerts a force on the induced current that opposes the change.
6. The presence of the iron core in a transformer allows the primary coil to produce a stronger magnetic field than with an air core. The iron core carries the magnetic flux from the primary coil through the secondary coil.

From Ideas to Implementation

1. The electric force acting on an electron in a uniform electric field is in the opposite direction to the field lines.
2. The magnetic force acting on a moving charge is perpendicular to both the velocity vector and the magnetic field direction.
3. For a constant intensity of light, the number of electrons released per second in the photoelectric effect decreases as the frequency increases.
4. For a constant frequency of light, the number of electrons released per second increases as the intensity of the light increases.
5. The Planck radiation curve has a peak since relatively few atoms in the wall of a hot object are vibrating at high frequencies (each sending out a high energy photon) and many are vibrating at lower frequencies (each sending out a low energy photon).
6. In the photovoltaic effect (in a solar cell) an electron in the valence band of the p-type semiconductor absorbs a photon (whose energy is greater than the band gap) creating a hole in the valence band and an electron in the conduction band. An electric field exists across the p-n junction and this pulls electrons to the n side where they can flow out of the cell if it is connected to a load resistor.

Quanta to Quarks

1. The scattering of a small number of alpha particles through a large angle by a thin gold foil is experimantal evidence for a small positively charged nucleus with most of the volume of the atom empty space.
2. The line spectrum of hydrogen is evidence for quantised energy levels in the hydrogen atom.
3. Chadwick collided neutrons with hydrogen and nitrogen atoms and measured the speed of each target atom after collision. The mass of the neutron was determined by applying the laws of conservation of momentum and kinetic energy to the elastic collisions.
4. Binding energy is the energy released when protons and neutrons combine to form a nucleus. Energy is released in nuclear fission because the total binding energy after reaction is greater than the total binding energy before reaction.
5. "mass and energy are both but different manifestations of the same thing", Einstein quote.
6. The anti-neutrino and electron given off in beta decay of a neutron share the released energy and momentum. In this process a down quark in a neutron is converted to an up quark by the release of a W minus boson which decays into an electron and an anti-neutrino. This decay happens as the nucleus is unstable due to it having too many neutrons for the number of protons present.

IB Physics Longitudinal Waves

A tutorial sheet of  longitudinal wave questions is given below.

1. A longitudinal progressive wave moving from left to right has a frequency f and wavelength λ. Two particles, P and Q, have equilibrium positions one-half a wavelength apart. At a certain instant P is at rest and is displaced to the left of its equilibrium position.(a) What is the amplitude of oscillation of P? (b) What is the displacement of Q from its equilibrium position?
2. Do we have nodes in longitudinal progressive waves?
3. In a longitudinal standing wave at which points in the pattern is the pressure greatest?
4. In a longitudinal standing wave at which points in the pattern is the density greatest?
5. In a longitudinal standing wave do all particles have the same frequency of vibration?
6. In a longitudinal standing wave are all of the particles vibrating in phase?
7. In a longitudinal standing wave the pressure mimima (rarefactions) are positions where the particles have zero displacement from their equilibrium position. Why is this?
8. Are the pressure maxima (compressions) at a position of zero particle displacement?
9. A closed pipe of length 1.5m is sounding its third harmonic. If the maximum possible displacement of a particle in the pipe from its equilibrium position is a what is the maximum displacement of a particle 0.25 m from the closed end of the tube? The speed of sound is 343 m/s and neglect the end correction.
10. Where would you hear a louder sound, at the anti-node or at the node of displacement of a standing wave?

HSC Physics Quanta to Quarks

With the old Quanta to Quarks elective being examined for the last time this November a list of true-false questions on concepts that are often misunderstood is given below. This list will be updated during the next six weeks.

Rutherford Model of the Atom

1. Rutherford's model of the atom has a central charge concentration made of protons and neutrons.
2. The alpha particles that bounce back from the gold foil hit the nuclei of the atoms in the foil.
3. Rutherford's model did not have electrons orbiting the nucleus in rings
4. In Rutherford scattering the number of alpha partices scattered through 60 degrees is one-half the number scattered through 30 degrees.
5. If the thickness of the gold foil is doubled the number of alpha particles scattered through each angle is halved.
6. In the Geiger and Marsden 1910 scattering experiment the number of alpha particles scattered through an angle greater than 90 degrees was 1 in 800.

Radioactivity

1. Alpha particles released in the decay of Ra-226 have different kinetic energies.
2. Beta particles given off in the decay of Sr-90 have the same kinetic energies.
3. Gamma rays are released when an electron makes a transition to a lower energy level in Co-60.
4. Gamma rays can be detected using a cloud chamber.
5. Alpha particle tracks in a cloud chamber are thicker and longer than those of beta particles.
6. In beta minus decay an electron is ejected from the nucleus.
7. Half-life is the time for exactly one half of the original number of nuclei to decay.
8. Technetium-99m is a radioisotope of half-life 6 h that emits gamma radiation and is used as a tracer in nuclear medicine.

Hydrogen Spectrum

1. The line spectrum of hydrogen is evidence for quantised energy levels in the hydrogen atom.
2. The longest wavelength in the Balmer series for hydrogen is 656.1 nm.
3. The shortest wavelength in the Balmer series for hydrogen is 364.5 nm.
4. The wavelengths in the Balmer series become closer together when placed in order from longest to shortest.
5. The four longest wavelengths in the Balmer series can be seen by the human eye.
6. The energy required to remove an electron from the ground state of the hydrogen atom is 13.6 eV.
7. The energy of the photon released when an electron makes a transition from n _i =5 to n _f =3 is 1.0 eV.
8. The shortest wavelength in a certain spectral series for hydrogen is 2.28 μm. The longest wavelength in this series is 7.46 μm.

Modifications of the Bohr Model of the Atom

1. The Bohr postulates can be applied to an atom with more than one electron.
2. The energy required to remove the electron from the ground state of a helium atom with one electron only is 54.4 eV.
3. The difference in intensity of spectral lines is explained using additional quantum numbers to n. This predicts extra states for the electron to exist in. This allowed the development of selection rules and the calculation of transition probabilites.
4. The state of the electron in the hydrogen atom is now described by 4 quantum numbers. These are n (1,2,3..), l (0,1,2,..n-1), m (-l, -2,-1,0,1,2,...l) and s (-1/2 or 1/2).
5. The Zeeman effect in hydrogen is the splitting of spectral lines that occurs when a magnetic field is applied to the gas. The magnetic field interacts with the orbiting electron creating extra energy levels allowing more electron transitions.In the Balmer series, this creates 2 extra spectral lines equally spaced on either side of the spectral line observed with no magnetic field.

Neutrons

1. When beryllium is bombarded with alpha particles a highly penetrating radiation is given off that can eject protons with considerable velocities from matter containing hydrogen.
2. Neutron scattering is a non-destructive technique to probe materials such as turbine blades for defects as neutrons have no charge and have a wavelength comparable to the spacing between atoms and so are diffracted producing an interference pattern from which the arrangement of atoms can be determined.

Heisenberg

1. The Heisenberg uncertainty principle limits us measuring the exact position of an electron.
2. Matrix mechanics uses matrices to represent observable quantities and the eigenvalues of the matrix are the observable values.
3. The uncertainty principle is a consequence of the wave nature of an electron.

Pauli

1. Pauli proposed in 1930 the existence of an uncharged particle of very small mass that carried energy and momentum to explain the continuous spectrum of beta decay. This was later called the neutrino.
2. The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers.

Fermi

1. Fermi found that slower moving neutrons could produce more radioactivity in silver than faster moving neutrons. He deduced that slower moving neutrons, produced by collisions in paraffin wax, were more easily captured than faster moving neutrons.
2. Fermi was in charge of the group that carried out the first sustained controlled fission reaction of U-235 using graphite blocks as a moderator and cadmium control rods on December 2 1942.

Particle Accelerators

1. The drift tubes in a linear accelerator increase in length to allow allow an alternating voltage of constant frequency to be be applied across each tube so that the speed of the beam increases.
2. The LHC uses superconducting magnets as these produce very strong magnetic fields using low currents.
3. A cyclotron uses magnetic fields to increase the speed of the charges.
4. A synchrotron uses a time varying magnetic field to allow for the increase in relativistic mass of a charge as it travels faster so that it can cross the dees at regular time intervals.

Standard Model

1. The mediator of the strong nuclear force is a gluon.
2. In beta decay the quark composition of the particles does not change.
3. The strong nuclear force holds protons and neutrons together.
4. The strong nuclear force holds quarks together.

HSC Physics Ideas to Implementation

With the old Ideas to Implementation topic being examined for the last time this November a list of true-false questions on concepts that are often misunderstood is given below. This list will be updated during the year.

Cathode Rays

1. A paddle wheel spins showing that cathode rays have momentum.
2. A paddle wheel will spin if the pressure in the tube is zero.
3. Cathode rays are not emitted when positive ions in a discharge tube impact on the cathode.
4. Cathode rays cause glass to phosphoresce.
5. Heinrich Hertz found that cathode rays could not travel through a metal foil.
6. Heinrich Hertz observed that cathode rays were deflected by an electric field.
7. When the pressure in a gas discharge tube is reduced the order of formation of structures in the tube is Faraday dark space, positive column, striated positive column, Crookes dark space, negative glow.
8. Dark spaces in a discharge tube are caused by destructive interference.
9. Cathode rays have their greatest speed in the bright areas.

Electric and Magnetic Fields

1. In J J Thomson's original experiment he used perpendicular electric and magnetic fields to give equal magnitude forces on a cathode ray causing them to move in a straight line.

Blackbody Radiation Curve

1. An example of a blackbody is a piece of iron painted black.
2. In the blackbody spectrum there are not many photons released at low frequencies.
3. In the blackbody spectrum there are many photons released at high frequencies.

Photoelectric Effect

1. The frequency of light is the number of photons passing a point in one second.
2. If the frequency of the light increases there are more photons passing a point in one second.
3. If the frequency of the light increases the intensity of the light remains constant.
4. The photoelectric current does not change if the intensity of the light is kept constant and the frequency is increased.
5. Heinrich Hertz found that when ultraviolet light was directed on a spark gap a spark was not produced when the width of the gap was increased.
6. Photoelectrons ejected by exposure to bright light have a greater maximum kinetic energy than those ejected by dimmer light of the same frequency.

Conduction in Metals

1. The crystal lattice is composed of positively charged ions. Conduction electrons are attracted to the lattice ions and this causes resistance in a metal.
2. Resistance in a copper wire is due to collisions between the conduction electrons and the stationary copper atoms in the wire.

Band Theory

1. The valence band in an insulator is not full.
2. Intrinsic silicon has no electrons in the conduction band at room temperature.
3. Conduction in intrinsic silicon is due to electrons moving in the valence band.

Bragg Experiment

1. The x-ray diffraction pattern produced by a crystal is a series of alternating bright and dark fringes.

Superconductors

1. Magnetic fields cannot pass through all superconductors.