A bubble in glass slab (µ = 1.5) when viewed from one side appears at 5 cm and 2 cm when viewed from the other side. Thickness of the slab is:

1. 3.75 cm

2. 3 cm

3. 10.5 cm

4. 2.5 cm

A ray of light travelling in the air has wavelength λ, frequency n, velocity v, and intensity I. If this ray enters into water then these parameters are λ', n', v' and I' respectively. Which relation is correct?
1.  λ = λ′
2.  n = n′
3.  v = v′
4.  I = I′

A beam of light composed of red and green rays is incident obliquely at a point on the face of a rectangular glass slab. When coming out on the opposite parallel face, the red and green rays emerge from: