Q. Refractive index of a rectangular glass slab is μ = √3. A light ray incident at an angle 60° is displaced laterally through 2.5cm. Distance travelled by light in the slab is
(a) 4 cm
(b) 5 cm
(c) 2.5√3 cm
(d) 3cm
Click to See Answer :
Ans: (b)
Sol:Angle of incidence = 60°
By applying Snell’s law ,
1×sin60 = √3×sinr
√3/2 = √3×sinr ,
sinr = 1/2
and r= 30°
By applying formula ,
Lateral Shift = t sin(i-r)/cosr
2.5 = tsin(60-30)/cos30
= t (tan30)
2.5 = t(1/√3)
t= 2.5 √3 cm
distance travelled by light in the slab
= t/cosr
= (2.5√3)/cos30 = 5 cm