Question

When violet light and yellow light shine on a metal surface, only one color produces an electric current. Write 3 - 4 sentences describing the effect of each light on the metal. Would increasing the intensity of either type of light have an effect on the current produced? How does quantization help to explain these observations? (6 points) Please don't write too long :)

Answer 1

Answer: voilet light has more frequency than the yellow light. Therefore voilet light has larger energy than the yellow light. Every metal has its electrons bound to it. Since, for the production of electric current, there needs to be the removal or ejection of electrons out of the metal surface. The flow of these electrons will then represent the electric current. Every metal has a minimum energy needed for the ejection of electrons out of its surface. This minimum energy required is known as the threshold energy and the corresponding frequency is known as the threshold frequency. That is why only one light out of the two produces electric current which satisfies the threshold energy condition. Therefore either only violet light will produce current or both violet and the yellow light will produce the current from a metal surface when shined on it.

(B) The increase in intensity increases the electric current only if it's frequency is greater than the threshold frequency. Because intensity has not the effect on the energy of the emitted electrons but it can only increase the number of the released electrons out of the metal surface.

(C) only quantization of light I.e the particle nature of light can explain the above observations. Because increasing frequency in wave nature of light has nothing to do with the energy of the emitted electrons. However on particle nature of light, increasing frequency implies increasing the energy of photons impinged on the metal surface and hence increases the energy of the emitted electrons.