A photosensitive material is at 9m to the left of the origin and the source of light is at 7 m to the right of the origin along x-axis. The photosensitive material and the source of light start from rest and move, respectively, with `8hatims^(-1)` and `4hatims^(-1)`. The ratio of intensities at `t=0` to `t-3 s` as received by the photosensitive material

Options

A. `16:1`
B. `1:16`
C. `2:7`
D. `7:2`

Answer

B

Explanation

The separation between source and photosensitive material at `t=0` is 16m. Therefore intensity received by photosensitive material at `t=0` is `I_0=(P)/((4pixx16^(2))`, where P is the power of source of light
At `t=3` s , the source is at `(15,0)` and detector is at `(19.0)`, so the separation between themis 4m.
`I_2=(P)/(4pixx4^2)`
so, `(I_1)/(I_2)=(1)/(16)`