A pulse of light of duration `100 ps` is absorbed completely by a small object initially at rest. Power of the pulse is `30 W` and the speed of light is `3xx10^8 ms^(-1)`. The final momentum of the object is :

Options

A. `0.3 xx 10^(-17)kg ms^(-1)`
B. `1.0 xx 10^(-17) kgms^(-1)`
C. `3.0 xx 10^(-17) kg ms^(-1)`
D. `9.0 xx 10^(-17) kg ms^(-1)`

Answer

B

Explanation

`{:("Energy incident",=" Power (time)"),(,=(30 mw) (100 ns)),(,=3xx10^(-9)):}`
So momentum `=E/c=(3xx10^(-9))/(3xx10^(8))=10^(-17) kg m//sec`.