Question

Yellow-orange light (? = 600 nm) passes through a single slit that is 1.50×10–4 m wide. Its diffraction pattern is displayed on a screen 0.900 m away from the slit. What is the distance from the first minimum on the right to the first minimum on the left?

Answer 1

For the first order minimum, the condition for diffraction is,
d sin =
Where d is the slit width and is the wavelength
sin = /d
= (600 x 10^-9) / (1.50 x 10^-4)
= 4 x 10^-3.

tan = h/D
Where h is the distance from the center of the diffraction pattern to the first minima and D is the distance to the screen.
h = D tan
For small angles, tan = sin = 4 x 10^-3
h = 0.9 x 4 x 10^-3
= 3.6 x 10^-3
Distance from the first minimum on the left to the first minimum on the right = 2h
= 2 x 3.6 x 10^-3
= 7.2 x 10^-3
= 7.2 mm