5.7 - Diffraction Grating

5.7 - Diffraction Grating

1. A plate with closely spaced slits ruled on it.

   • Parallel beam of monochromatic light transmitted in only certain directions.
     • Light passing through each slit is diffracted
     • Diffracted light waves reinforce light from adjacent slits in specific directions, cancelling out all other directions
     • Central beam (zero order) is the same direction as the incident beam

2. Angle of diffraction

   • Increases with light of longer wavelength
   • Increases with closer slits.

3. Diffraction equation

4. Maximum number of orders is d/ λ, rounded to nearest integer.

5. Spectra

   • Continuous Spectra
     • From deep violet to deep red
     • Hotter the light source, the shorter the wavelength of the brightest part of the spectrum
   • Line emission spectra
     • Glowing gas emits light at specific wavelengths
       • Wavelengths are characteristic of the element that produces the light
         • Elements are identifiable
   • Line absorption spectra
     • A continuous spectrum with narrow dark lines at specific wavelengths.
     • Due to elements in glowing gas
       • Absorbs light at the wavelength they emit at

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