Interference

Interference l2- l1 = m λ (Constructive) l2- l1 = (m+1/2) λ (Destructive) m = 0,1,2,3,4,………

Thin film interference 2t = (m+1/2) λfilm Constructive 2t = m λfilm Constructive 2t = (m+1/2) λfilm Destructive λfilm = nvac /nfilm

Phase Change If light is reflected from a surface where n1 > n2 there is a ½ λ phase shift. Zero or One phase shift 2t = m λfilm Constructive 2t = (m+1/2) λfilm Destructive One phase shift 2t = (m+1/2) λfilm Constructive 2t = m λfilm Destructive

Light of wavelength 600nm impinges upon a soap film (n = 1 Light of wavelength 600nm impinges upon a soap film (n = 1.4) on top of glass (n = 1.5) . What is the smallest thickness of film that will produce constructive interference? (Assume the index of refraction of air is n= 1.0)

Light of wavelength 600nm impinges upon a soap film (n = 1 Light of wavelength 600nm impinges upon a soap film (n = 1.4) on top of plastic (n = 1.3) . What is the smallest thickness of film that will produce constructive interference? (Assume the index of refraction of air is n= 1.0)

Double slit Sin θ = m λ / d Constructive (bright) Sin θ = (m + ½) λ / d Destructive (dark)

A double slit experiment is setup using light of wavelength, 600nm with a slit spacing of 2x10-5m. If the screen is located 5m from the slits how far from the pattern middle is the first bright, dark spot located?

Single slit/Barrier Sin θ = m λ / w Dest. (dark) m = 1,2,3,4,………

Diffraction grating Sin θ = m λ / d Const. (bright) d = dist. between slits d = 1/# of slits per m.

Missing bright spots in the double slit pattern Sin θ = m λ / d Constructive (bright) Single slit Sin θ = m λ / w Destructive (dark)