Diffraction Grating
DATA TABLE:
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λ of laser (nm)
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L (m)
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Several Δx Values (m)
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Δxavg
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θ (tan -1 Δxavg /L)
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Part 1:
Calculations:
- Convert λ, wavelength, of laser from nm to m. Remember 1 nm = 1 x 10 -9 m.
- Average all Δx values to get one Δxavg.
- Calculate the angle θ from tan θ = Δxavg/L.
- Find sin θ.
- Solve for d using n λ = d sin θ; i.e. d = n λ/sin θ.
- Use d to find d-1, i.e. how many lines there are per mm of diffraction grating.
Part 2:
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λ of laser (m)
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Distance to wall (m)
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Measured values of n (m)
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Average change in n (m)
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Calculated theta
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633 * 10^-9
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Calculate theta: tan^-1 (average distance between dots on wall) / (distance from card to wall)
Calculate d: wavelength / sin theta
Calculate number of grooves per mm: 1/d
Calculate number of grooves on CD = (grooves /mm) (radius of CD- grooved part only)