Question

Light from a laser with a wavelength of 4.2×10^-7 m shines through two slits and forms an interference pattern on a screen 1.8 m away. You measure the separation between the central bright fringe and the m=2 bright fringe to be 0.03 m.

1. What is the angle for the m=2 bright fringe (in degrees)?

2. What is the separation between the two slits?

3. What is the angle for the m=1 bright fringe?

4. What is the distance from the central bright fringe to the m=1 bright fringe?

5. What is the angle for the m=1 dark fringe?

6. What is the distance from the central bright fringe to the m=1 dark fringe?

Answer 1

Given that,

wavelength of light, = 4.2*10^(-7) m

Length of screen, L = 1.8 m

distance from central fringe , x = 0.03 m

(2)

separation between the two slits,

d = m**L / x

d = 2*4.2*10^(-7)*1.8 / 0.03

d = 50.4*10^(-6) m

d = 50.4 um

(1)

angle for the m = 2 bright fringe,

sin() = m / d

sin() = 2*4.2*10^(-7) / 50.4*10^(-6)

= 0.954 deg

(3)

angle for the m = 1 bright fringe,

sin = 1*4.2*10^(-7) / 50.4*10^(-6)

= 0.477 deg

(4)

distance from the central bright fringe to the m = 1 bright fringe,

x = 0.03 / 2

x = 0.015 m