1) The pulse of light duration 100 ns is absorbed completely by a small object initially at rest. Power of pulse is 30mV and the speed of light is 3 x108 ms-1. The final momentum of object is A) $0.3\times 10^{-17}kg-ms^{-1}$ B) $1.0\times 10^{-17}kg-ms^{-1}$ C) $3.0\times 10^{-17}kg-ms^{-1}$ D) $9.0\times 10^{-17}kg-ms^{-1}$ Answer: Option BExplanation:final momentum of object = Power x time / speed of light = $\frac{30\times 10^{-3}\times 100\times10^{-9}}{3\times 10^{8}}=1.0\times 10^{-17}kg-m/s$
