A plane polarized light is incident perpendicularly on polaroid. Taking incident light as an axis polaroid is rotated with an angular speed `pi rads^(-1)`. If light energy incident in 1s is 4 mJ. How much energy will emerge after one rotation ?

Explanation

`int_(0)^(T)cos^(2)omegatdt=(pi)/(omega)`
Here, `I_(0)=4mJ=4xx10^(-3)J,omega=pi" rad "s^(-1)`
`I=I_(0)cos^(2)omegat`
`:.` Energy emerging during one rotation,
`=int_(0)^(T)I_(0)cos^(2)omegatdt`
`=(I_(0)pi)/(omega)`
`=(4xx10^(-3)xxpi)/(pi)`
`4xx10^(-3)J`