Lesson Plan: Diffraction Gratings Physics • 9th Grade

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to calculate the positions of the principal maxima of intensity in diffraction patterns generated by diffraction gratings.


Students will be able to

  • use the small angle approximation to relate the angular distance, 𝜃, measured from the center of a diffraction grating with a line spacing 𝑑 to a diffraction maximum of order 𝑛 that is produced when light waves of wavelength 𝜆 pass through the grating, applying the equation 𝑛𝜆=𝑑𝜃sin,
  • identify the number of equally separated thin slits through which monochromatic light waves have propagated by inspection of the diffraction pattern produced by the waves.


Students should already be familiar with

  • two-slit interference patterns,
  • single-slit diffraction patterns.


Students will not cover

  • intensity calculations.

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