Double slit vs diffraction grating similarity’s and differences
Double Slit
Diffraction
Differences
Differences
Results are bands of fringes
Similarity’s
Source of light
Results are spots that spread out from the centre
Laser
One colour (one frequency/wavelength), “Monochromatic source”
One wavelength
Blue
Green
300 nm
Red
650 nm
350 nm
Must be coherent = Constant phase difference
Only two slits
Multiple slits
Equation:
W = Width of fringe (M)
lambda = wavelength (M)
D = Distance between slits and screen (M)
S = Slit separation (M)
Equation:
n = Order of fringe (M)
lambda = wavelength (M)
d = Diffraction gradient separation [same as S] (M)
sin(theta) = angle of a bright fringe from the centre