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# The energy $E$ and the momentum $p$ of photon are given by $E=hn\: and\: p=h/\lambda$ respectively. The velocity of photon will be

$\begin {array} {1 1} (a)\;E/p & \quad (b)\;Ep \\ (c)\;(E/p)^2 & \quad (d)\;(E/p)^{\large\frac{1}{2}} \end {array}$

Can you answer this question?

Ans : (b) E/p
velocity, $v = n\lambda, \lambda=h/p$
$\Rightarrow v=E/p$

answered Dec 24, 2013
edited Mar 13, 2014