Question

A ray of light strikes a flat, 2.00-cm-thick block of glass (n = 1.26) at an angle of 0 = 14.8° with respect to the normal (see figure below). 2.00 cm (a) Find the angle of refraction at the top surface and the angle of incidence at the bottom surface. (b) Find the refracted angle at the bottom surface. (c) Find the lateral distance d by which the light beam is shifted. cm (d) Calculate the speed of light in the glass. m/s (e) Calculate the time required for the light to pass through the glass block. S

Answer 1

1) using snell's law :

ni*sin(i) = n2*sin(r)

sin(r) = sin(14.8)/1.26

sin(r) = 0.207

r1 = 11.94 degrees

2) refracted angle at bottom surface = incident angle at upper surface

So,

r2 = 14.8 degrees.

3) lateral shift = thickness*sin(i-r1) /cos(r)

D = 2*sin(2.86)/cos(11.94)

D = 0.1019 cm

4) v = c/n

v = 3*10^8/1.26

v = 2.38*10^8 m/s

5) distance travelled by light in slab :

X = 2/cos(11.94)

X = 2.044 cm

Time required = X/v

T = 2.044*10^-2/2.38*10^8

Y = 0.859*10^-10 seconds