Question

Which of the following are the correct postulates of the quantum theory of light?
(A). Each photon of frequency v has the energy hv, the same as Planck’s energy.
(B). The higher v, the greater the photon energy hv.
(C). Blue color has lower energy than green color.
(D). Changing the intensity of the incident light beam will change the frequency v of the photon.
Choose the correct answer from the options given below:

• A. (A), (B), and (C) only
• B. (A), (B), and (D) only
• C. (A) and (B) only
• D. (A) and (D) only

Hint:

The energy of the photon is given by E=hv where h is planck’s constant and v is the frequency. The frequency is not dependent on the intensity of light, which is why higher frequency light such as blue light has more energy than red light.

Answer 1

The Correct Option is C

Quantum theory of light proposes that light is comprised of individual packets of energy called photons.
• Photon energy: Each photon of frequency v has energy E=hv (where h is Planck’s constant), it is the same as Planck’s energy.
• Frequency and energy relationship: Photon energy is directly proportional to the frequency (v); the higher the frequency, the greater the photon energy.
• Color and frequency: Blue light has a higher frequency than green light, meaning blue has higher energy than green light.
• Intensity and Frequency: Changing the intensity of light means changing the number of photons, and has no effect on the frequency of each photon.
Therefore, options A and B are correct.