Question

Momentum of a photon of frequency v is:
1. hv
2. hcv
3. hv/c
4. hc/v

Answer 1

Correct Answer - Option 3 : hv/c

CONCEPT:

Photon:

• According to Einstein's quantum theory light propagates in the bundles (packets or quanta) of energy, each bundle is called a photon and possessing energy.

The energy of photon:

• The energy of each photon is given by

\(⇒ E = h\nu = \frac{{hc}}{\lambda }\)
Where c = Speed of light, h = Plank's constant = 6.6 × 10–34 J-sec, ν = Frequency in Hz, λ  = Wavelength of light

The momentum of the photon:

\(⇒ p = m \times c = \frac{E}{c} = \frac{{h\nu }}{c} = \frac{h}{\lambda }\)

• The relation between the energy and momentum of the photon is given by

\(⇒ p=\frac{E}{c}\)

EXPLANATION:

• From the above, it is clear that the momentum of a photon of frequency v is:

⇒ p = hv/c