Diffraction Lab

The purpose of this investigation is to determine what factors change the diffraction pattern.

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When light passes through a diffraction grating, something remarkable happens.

A diffraction grating is made of a transparent material that contains thousands of evenly spaced tiny slits. Because the slits are evenly spaced, the light waves that pass through interfere with one another. At certain angles, the waves line up perfectly (they are in phase) and reinforce each other. When this happens, a bright image - called a fringe - is formed. This occurs when the path difference between light from adjacent slits equals a whole number of wavelengths.

The condition for bright fringes is given by:

Where:

• d = distance between adjacent slits (grating spacing)

• θ = angle between the bright fringe and the normal (straight out from the grating)

• λ = wavelength of the light

• m = order number (0, 1, 2, 3, …)

Understanding the Fringe Orders

• m = 0 is called the 0th order maximum.
  This is the central bright spot where light goes straight through.
  It always appears at θ = 0°
  

• m = 1 is the 1st order maximum.
  This is the first bright spot on either side of the center.
  

• m = 2, 3, 4 . . . are the 2nd, 3rd, 4th, , , , , order maxima
  These are the second, third, and fourth spot on either side of the center.

Download and complete the Diffration Lab Report

Wavelength, λ, of the red laser is 650 nm

Wavelength, λ, of the green laser is 532 nm