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Assertion : A photon has no rest mass, yet it carries definite momentum.
Reason : Momemtum of photon is due to its energy and hence its equivalent mass.
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Reason : Momemtum of photon is due to its energy and hence its equivalent mass.
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If both assertion and reason are true and reason is the correct explanation of assertion
Equivalent mass of photon $(m)$ is given from equation
$E=m c^2=h v \therefore m=\frac{h v}{c^2}$
Where $E$ is energy, $m$ is mass, $c$ is speed of light, $h$ is Planck's constant, $v$ is frequency.
$\therefore \quad$ Momentum of photon $=\frac{h v}{c^2} \times c=\frac{h v}{c}$
$E=m c^2=h v \therefore m=\frac{h v}{c^2}$
Where $E$ is energy, $m$ is mass, $c$ is speed of light, $h$ is Planck's constant, $v$ is frequency.
$\therefore \quad$ Momentum of photon $=\frac{h v}{c^2} \times c=\frac{h v}{c}$
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