Answer:
(a) 40.6 degree
Explanation:
When refraction takes place from slab to water, the critical angle is 60 degree.
Use Snell's law
refractive index of water with respect to slab
[tex]\mu _{w}^{s}=\frac{Sin60}{Sin90}[/tex]
[tex]\frac{\mu _{w}}{\mu _{s}}=0.866[/tex]
[tex]\frac{1.33}{\mu _{s}}=0.866[/tex]
μs = 1.536
Now for slab air interface, the critical angle is C.
[tex]\mu _{a}^{s}=\frac{SinC}{Sin90}[/tex]
[tex]\frac{\mu _{a}}{\mu _{s}}=\frac{SinC}{Sin90}[/tex]
1 / 1.536 = Sin C
C = 40.6 degree