DIFFRACTION OF LIGHT DIFFRACTION OF LIGHT

INTERFERENCE When two light sources interfere with each other. Light intensity is reinforced at bright bands. Light intensity is lost at dark bands

Iridescence- interference of light produced by a thin layer of a substance on a surface

DIFFRACTION Producing an interference pattern with only one light source. Light rays move around a barrier and interfere producing bright bands and dark bands.

DIFFRACTION Ridges in feather diffract white light, separating it into different colors. Small grooves on CD diffract light.

DOUBLE SLIT DIFFRACTION Constructive interference Constructive interference m=0 Destructive interference Destructive interference

FORMULA λ/d = x/L λ = wavelength (m) d = distance between slits (m) X = distance from central maximum to first order bright line (m) L = distance from the slits to the screen (m)

Sample problem First order image X light λ λ λ Central Maximum Light falls on 2 slits that are 1.9 x 10-4cm apart. A first order bright line is formed 22cm from the central maximum. The distance from the slits to the screen is 60cm.

A) Find the wavelength of light L = 60cm =0.6m x = 22cm = 0.22m d = 1.9 x 10-4cm = 1.9 x 10-6m λ/d = x/L λ / 1.9 x 10-6 = 0.22 / 0.6 0.6λ = 4.18 x 10-5 λ = 6.96 x 10-7m

B) What color light is it? Use v = f λ v = 3.0 x 108m/s λ = 6.96 x 10-7m 3.0 x 108m/s = f (6.96 x 10-7m) f = 4.3 x 1014Hz Red light