Question

eG GO In Fig. 35-51a, the waves along rays 1 and 2 are initially in whase with the same wavelength 1 in air. Ray 2 goes through a ma- mial with length L and index of refraction n. The rays are then reflected by mirrors to a common point P on a screen. Suppose that we can vary n from n = 1.0 to n = 2.5. Suppose also that, from n = 1.0 to n = ns = 1.5, the intensity I of the light at point P varies with n as given in Fig. 35-51b.At what values of n greater than 1.4 is intensity I (a) maximum and (b) zero? (c) What multiple of 1 gives the phase difference between the rays at point P when n = 2.0? Screen KL Ray 2 Ray 1 (a) Figure 35-51 Problems 86 and 87.

Answer 1

25 noto to na 15, 1. 4 than warlength ways Path length diffeure is if I havelength Path length differences & (Wavelength say 2- = x (L/W/M) - 42) = n2-L=(n-1) L We have (n-1) L = Path length diff PLD = 1/2 When n=14 (14-1).L = 0.82= 1/2 - NL = 08 (n-1) L= H=/L=0.8 n=0.8+ In=1.8 ✓ b) PLD: 32) (n-1) L = 3/2 n-L= 3/2 x (0-8) 0-15:2 12+1=22 Al n= 20 PLO- (2-1)2 = 11 but L=N/0.8 PLD = 1/0.80 = 1.25X So the factor & (1.25 6