The time taken by the sunlight to reach the bottom of a tank of depth 4.5m filled completely with water is ....... ns. The refractive index of water is `4/3`

Options

A. 2
B. 1.5
C. 20
D. 200

Answer

B, C

Explanation

`n=c/v=c/d=(ct)/(d)`
`therefore t =(nd)/(c)`
`=4/3xx(4.5)/(3xx10^8)=(18)/(9)xx10^(-8)=2xx10^(-8)` second
`therefore t=20xx10^(-9)` second = 20 ms