A pulse of light of duration 100 ns is absorbed completely a small object initially at rest…

Q: A pulse of light of duration 100 ns is absorbed completely a small object initially at rest. Power of the pulse is 30 mV and the speed of light is 3×108 ms-1. The final momentum of the object is

(a)0.3×10-17 kg-ms-1

(b)1.0×1017 kg-ms-1

(c)3.0×1017 kg-ms-1

(d)9.0×1017 kg-ms-1

Ans: (b)

Sol: Final Momentum of the Object $\large = \frac{Power \times time}{Speed \; of \; light}$

$\large = \frac{30 \times 10^{-3}\times 100 \times 10^{-9}}{3 \times 10^{8}}$

= 1.0 × 10-17 kg m/s