Question

The equation \( E = pc \), (where \( E \) and \( p \) are energy and momentum respectively) is valid: 
 

• A. for an electron as well as for a photon.
• B. for an electron but not for a photon.
• C. for a photon but not for an electron.
• D. neither for an electron nor for a photon.

Hint:

The equation \( E = pc \) applies only to massless particles such as photons.

Answer 1

The Correct Option is C

The equation \( E = pc \) applies to massless particles like photons, where \( E \) is the energy, \( p \) is the momentum, and \( c \) is the speed of light. For particles with mass, such as electrons, the correct relationship is \( E^2 = (pc)^2 + (mc^2)^2 \).