HSC Physics Ideas to Implementation

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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.