Diffraction Patterns Due To A Single Slit And A Circular Aperture
Concepts to remember on Diffraction Patterns Due to a ‘SingleSlit’ and a ‘Circular Aperture’:
SingleSlit:
 Diffraction is the spread of light when passing through a slit.
 Diffraction produces a pattern of bright and dark bands.
 Central Bright spot is inversely proportional to the slit’s width. $$W=2λL/a$$
 Dark band $$sinθ_n = nλ/a$$ where n=1,2,3,…
 θn is the angle of the nth dark band from the center.
 λ is the wavelength of light.
 a is the width of the slit.
Circular Aperture:

Circular apertures produce central bright circles

First bright ring of radius=$$2.44λf/D$$, where:

λ is the wavelength of light.

f is the focal length of the lens.

D is the diameter of the circular aperture.

Dark rings are located by:
$$J_\alpha(x_\alpha)=0, x_\alpha=k\pi $$
 $$J_\alpha(x_\alpha)$$ is the Bessel function of the first kind of order α.
 $$x_\alpha$$ is the argument of the Bessel function.
 k is an integer (1, 2, 3,…).