A small bulb is placed at the bottom of a tank containing water to a depth of 1m. Find the critical angle for water air interface , also calculate the diameter of the circular bright patch of light formed on the surface of water. [ R.I of water =4/3]

Explanation

Given : `n=4//3` , C=? , d=1m , `n=1//sinC`
`sin C=1//n rArr sin C=1/(4//3)=3/4 rArr C = sin^(-1) (3//4)`
`C=48.6^@`
W.K.T. `r/h`=tan C
tan C x h =r
tan `48.6^@` x 1 m =2
r=1.1343 x 1
r=1.1343
d=2r=2 x 1.1343
d=2.2686 m