physics six marker questions

Question 1

Describe the phenomenon of Stopping potential?

Answer 1

1. Photons release electrons at the photocathode which causes a current
2. The energy of the energy of the electrons is greater than the work function of the photocathode
3. Electrons are released with a variety of kinetic energies
4. Electrons with smaller kinetic energy are stooped at a lower potential difference
5. The potential difference acts against the electrons motion
6. Reaches a point where all the electrons have stopped and have reached their stopping potential

Question 2

Describe the photoelectric effect and comment on what conclusions can be drawn from it?

Answer 2

1. Particle theory of light implied by the use of E=hf (discrete quanta of energy)
2. greater the frequency greater the kinetic energy of the photoelectrons
3. Lower frequency results in smaller kinetic energies or no photoelectrons being emitted
4. Energy normally depends on intensity is proportional to amplitude squared if a wave
5. More intensity should give off more photoelectrons with a greater kinetic energy
6. only gives off more electrons
7. waves are continuous, so if enough energy is absorbed over time a change should be seen.

Question 3

When light of a certain frequency is shone on a particular metal surface, electrons are emitted with a range of kinetic energies.

Answer 3

1. energy is needed to remove an electron from the surface
2. light consists of photons, each energy e=hf
3. one photon is absorbed by one electron
4. an electron can escape if its energy is greater than the work function
5. kinectic energies of the emitted electrons cannot be greater that hf-the work function
6. the work function is the minimum energy required for the electron to leave the metal.