Question

In which of the following phenomena the photon picture is required? (A) Energy distribution in black body radiation (B) Compton scattering (C) Photoelectric effect (D) all of the above

Short answer

The photon picture is required in all of the given phenomena: (A) Energy distribution in black body radiation, (B) Compton scattering, and (C) Photoelectric effect. Therefore, the correct answer is (D) all of the above.

Step-by-step solution

(A) Energy distribution in black body radiation

Black body radiation is the radiation emitted by a perfect absorber and emitter known as a black body. The energy distribution of black body radiation obeys Planck's radiation formula, which can be derived using the concept of photons. In this case, the photon picture is required since it helps to explain the quantized nature of the energy distribution, the ultraviolet catastrophe, and the Planck's constant.

(B) Compton scattering

Compton scattering refers to the scattering of high-energy photons (typically X-rays) off free charged particles, such as electrons. The scattered photon experiences a decrease in energy, and this phenomenon can be best explained using the photon picture. The energy and momentum conservation equations in the Compton scattering process involve the properties of photons and their interactions with electrons.

(C) Photoelectric effect

Photoelectric effect is the phenomenon in which electrons are ejected from the surface of a material when it is exposed to light of a certain frequency or higher. The photon picture is essential in explaining the photoelectric effect, as it accounts for the quantized nature of light energy and the dependence of electron ejection on the frequency of incident light. The photoelectric effect was one of the key experiments that led to the development of the photon concept.

Conclusion

Based on our analysis of each phenomenon, the photon picture is required in each of the given options (A, B, and C). Therefore, the correct answer is (D) all of the above.