Class 12 NEET Physics Optics Questions Part 1

Applying Snell's law of refraction at A,
we get
µ=

sin‌i

sin‌r

=

sin‌45°

sin‌r

∴ ‌sin‌r=

1

√2

µ
∴r=sin−1(

1

√2µ

) .......(i)
Applying the condition of total internal reflection at B, we get
ic=sin−1(

1

µ

) ......(ii)
where ic is the critical angle.
Now, r+ic=90°=

π

2

∴ sin−1

1

√2µ

=

π

2

−sin−1

1

µ

or, sin−1

1

√2µ

=cos−1

1

µ

∴

1

√2µ

=

√µ2−1

µ

or

1

2

=µ2−1
∴µ=√

3

2