When a glass slab is placed on a cross made on a sheet, the cross appears to be raised by `1cm`. The thickness of the glass is `3cm`. The critical angle for glass is

Options

A. `sin^(-1)(0.33)`
B. `sin^(-1)(0.5)`
C. `sin^(-1)(0.67)`
D. `sin^(-1)((sqrt(3))/2)`

Explanation

(c) We can write shift `1=3(1-1/(mu))`
`implies 1-1/(mu)=1/3`
or `1/(mu)=1-1/3=2/3impliesmu=3/2`
Now, `1/(sin i_(c))=3/2impliessin i_(c)=2/3`
or` i_(c)=sin^(-1)(2/3)impliesi_(c)=sin^(-1)(0.67)`