Question

A ray of light strikes a flat, 2.00-cm-thick block of glass (n = 1.35) at an angle of θ = 33.0° with respect to the normal (see figure below). 2.00 ㎝ (a) Find the angle of refraction at the top surface and the angle of incidence at the bottom surface 24.44 Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error.。 (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 (e) Calculate the time required for the light to pass through the glass block.

Answer 1

Soluiton:

a) Using snell's law ,

=> na sinθi = ng sinθr

=> sinθr = na sinθi / ng (Taking na refrective index of air = 1)

=> sinθr = sin(33) / 1.35

=> θr = 23.793 degree

b) The angle of emergence will be equal to the angle of incidence.

=> The refracted angle = 33 degree

c) Using d = L / cosθr x sin(33-23.793)

=> d = 2 / cos 23.793 x sin(9.207)

=> d = 0.3497 cm

d) Using v = c / ng

=> v = 3 x 10^8 / 1.35

=> v = 2.22 x 10^8 m/s

e) distance travelled by light

=> h = l / cos23.793

=> h = 2.18577 cm

time = h / v

=> time = 2.18577 x 10^-2 / 2.22 x 10^8

=> time = 0.9845 ns