Question

According to photon theory of light which of the following physical quantities associated with a photon do not / does not change as it collides with an electron is vacuum:

• A. Energy and momentum
• B. Speed and momentum
• C. Speed only
• D. Energy only

Answer 1

The correct option is A Energy and momentum

Under the photon theory of light, a photon is a discrete bundle (or quantum) of electromagnetic (or light) energy. Photons are always in motion and, in a vacuum, have a constant speed of light to all observers, at the vacuum speed of light (more commonly just called the speed of light) of $c=2.998\times {10}^{8}m/s$

According to the photon theory of light, photons .

move at a constant velocity, $c=2.9979\times {10}^{8}m/s$ (i.e. "the speed of light"), in free space

have zero mass and rest energy.

Carry energy and momentum, which are also related to the frequency $\mu$ and wavelength $\lambda$ of the electromagnetic wave by $E=h\mu$ and $p=\frac{h}{\lambda }.$

Can be destroyed/created when radiation is absorbed/emitted.

Can have particle-like interactions (i.e. collisions) with electrons and other particles, such as in the Compton effect