Question

Which of the following is the incorrect statement regarding photons?
A. Photon exerts no pressure
B. Photon energy is \[h\nu \]
C. Photon rest mass is zero
D. None of these

Answer 1

Hint: The energy of the photon is defined as the energy carried out by a single photon. The amount of energy of this photon is directly proportional to the photon's electromagnetic frequency and is inversely proportional to the wavelength. The higher the photon's frequency, the higher will be its energy.

Complete step by step solution:
Let’s have a look at each of the statements to find out whether they are correct or not.
If we see the first option.
The photon moves with a velocity of light and has an energy of\[h\nu \]. Then the pressure exerted by the photon is given by,
\[P = \dfrac{I}{c}\]
Here, I is the intensity of light and c is the speed of light.
This shows that the photon exerts pressure.

Secondly, whenever an electron or an atom jumps from the higher energy state to the lower energy state, a packet of light is emitted known as a photon and it has energy associated with it. The energy of a photon is,
\[E = h\nu \]
Hence, the photon has the energy of \[h\nu \]. If we consider the third option. They have given that the rest mass of the photon is zero. That is the energy that is stored inside a stationary particle as a result of its mass. Therefore, the incorrect statement is that a photon exerts no pressure.

Hence, option A is the correct answer.

Note: Photon is the smallest packet (quanta) of energy and by the particle nature of light, we can say that the light behaves as particles and this is confirmed by the photoelectric effect, but according to the wave nature of light, light behaves as waves and is confirmed by phenomena like reflection, and refraction, etc.