Q 9.17 (b)    What is the answer if there is no outer covering of the pipe?

                        

Answers (1)

In the case when there is no outer layer,

Snell's law at glass-air interface(when the ray is emerging out from the pipe)

\mu _{glass}sini'=1sin90

sini'=\frac{1}{\mu_{glass}} = \frac{1}{1.68}=0.595

i'= 36.5

refractive angle r corresponding to this = 90 - 36.5 = 53.5.

 the angle r is greater than the critical angle

So for all of the incident angles, the rays will get total internally reflected.in other words, rays won't bend in air-glass interference, it would rather hit the glass-air interference and get reflected 

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