What was Young's double slit experiment?

Light is directed towards two slits and an interference pattern is observed. 


Bright fringes are formed where the light interferes constructively.

Dark fringes are formed where the light interferes destructively.

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Describe the interference pattern produced by the double slit experiment with monochromatic light.

  1. Bright central maximum
  2. Evenly spaced fringes on either side of the central maximum
  3. Intensity of fringes decreases as distance from central maximum increases
  4. All fringes are the same width

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What is the path difference required for constructive interference to occur?

λ\lambda  OR  mλ\lambda  


m = any positive integer

λ\lambda = wavelength (m) 


Constructive interference will occur when the path difference is any number of whole wavelengths.

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What is the equation linking fringe spacing (w), wavelength (λ\lambda), distance to the screen (D) and slit spacing (s)?

w = sλD


w = fringe spacing (m)

λ\lambda= wavelength (m)

D = distance form slits to screen (m)

s = slit spacing (m) 

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