GCSE Physics Question Analysis Topic: Physics - Photoelectric Effect
Exam Question:
(a) Why photoelectric effect cannot be explained on the basis of wave nature of light? Give reasons.
(b) Write the basis features of photon picture of electron magnetic radiation on which Einstein's photoelectric equation is based.
Answer:
For GCSE Physics, you should know:
(a) There are several reasons:
i. The instant ejection of photoelectrons
ii. The presence of a threshold frequency for a metal surface
iii. Kinetic energy from the emitted electrons is independent of the light intensity, instead depending on the frequency.
(b) The basic features are:
i. when interacting with matter, radiation behaves as if it consisted of photons.
ii. Each photon has energy E = hv and momentum p = hv / c. (c being the speed of light)
iii. All photons of light of a particular frequency v, or wavelength λ, have the same energy E = hc / λ and the momentum p = hv / c.
iv. By increasing the light intensity of a given wavelength, there is only an increase in the photons per second crossing an area, with each photon carrying the same energy. As a result, the photon energy is independent of intensity of radiation
v. Photons are electrically neutral. Electric and magnetic fields do not deflect them.
vi. In a collision between a photon and particle, the total energy and momentum are conserved. Strangely, however, the number of photons may not be observed.
Work hard for your GCSE Physics examination!
End of analysis. Great!
