• # question_answer A photon of wavelength 4400 $\overset{\text{o}}{\mathop{\text{A}}}\,$ is passing through vacuum. The effective mass and momentum of the photon are respectively  A) $5\times {{10}^{-36}}kg,\,\,1.5\times {{10}^{-27}}\,kg\text{-}m/s$ B) $5\times {{10}^{-35}}kg,\,\,1.5\times {{10}^{-26}}kg\text{-}m/s$ C) Zero, $1.5\times {{10}^{-26}}\,kg\text{-}m/s$ D) $5\times {{10}^{-36}}kg,\,1.67\times {{10}^{-43}}kg\text{-}m/s$

[a] $p=\frac{h}{\lambda }=\frac{6.6\times {{10}^{-34}}}{4400\times {{10}^{-10}}}=1.5\times {{10}^{-27}}kg.m/s$ and mass $m=\frac{p}{c}=\frac{1.5\times {{10}^{-27}}}{3\times {{10}^{8}}}=5\times {{10}^{-36}}kg$