Find the energy stored in a 60 cm length of a laser beam operating at 4 m W.

Options

A. `8xx10^(-12) J`
B. `0.8xx10^(-12) J`
C. `0.008 xx 10^(-12) J`
D. `80 xx 10^(-12) J`

Answer

A

Explanation

`t = (60xx10^(-2))/(3xx10^(-12)) = 2xx10^(-9)sec`
`E = Pt = 4 xx 10^(-3) xx 2xx10^(-9) = 8xx10^(-12) J`