http://www.ck12.org Chapter 15. Diffraction and Interference of Light
Just as in double slit interference, a pair of similar triangles can be constructed in the interference pattern. The
pertinent values from these triangles are the width of the slit,w, the wavelength,λ, the distance from the central
bright spot to the first dark band,x, and the distance from the center of the slit to back wall,L. The relationship of
these four values is
λ
w=
x
Lorλ=wx
L.Example Problem:Monochromatic light of wavelength 605 nm falls on a slit of width 0.095 mm. The slit is located
85 cm from a screen. How far is the center of the central bright band to the first dark band?
Solution:x=λwL=(^6.^05 ×^10
− (^7) m)( 0. 85 m)
( 9. 5 × 10 −^5 m) =^0.^0054 m
Summary
- Interference patterns can also be produced by single slits.
- In the case of a single slit, the particles of medium at both corners of the slit act as point sources, and produce
circular waves from both edges. - The wavelength can be determined by this equation:λw=xLorλ=wxL.
Practice
Question