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Photon of frequency u has a momentum associated with it. If c is the velocity of light, the momentum is

Asked in AIEEE 2007 · Photon energy, momentum and mass

(1) (h u)/c
(2) u/c
(3) h u c
(4) (h u)/(c²)

Answer: (1) (h u)/c

Step-by-step solution

A photon carries energy E=h u and travels at c.

For a massless particle, E=pc.

p=E/c=(h u)/c.

Why the other options are wrong

(2) comes from drops Planck's constant, leaving something that is not even a momentum
(3) comes from multiplies by c where the relation divides by it
(4) comes from is E/c², which is the photon's equivalent mass, not its momentum

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