What is the name given to the beam of light that travels through the diffraction grating without changing direction?

Zero order

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What is meant by the 1st order angle?

The angle between the 1st order beam and the zero order beam.

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What is the equation linking grating spacing (d), angle (θ\theta), order number (n), and the wavelength of light (λ\lambda)?

d sin(θ) = n λ


d = grating spacing (m)

θ\theta = angle between order and zero order (°)

n = order number

λ\lambda = wavelength (m)

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What is the relationship between the number of slits per metre (N) and the slit spacing (d) for a diffraction grating?

N = d1​


The number of slits is also sometimes expressed as number of slits per mm. In this case 1 would become 1 x 10-3.

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How can the maximum observable order number for light passing a diffraction grating be determined?

  1. Substitute an angle of 90° into the diffraction grating equation.
  2. Solve to find n.

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Give some precautions that should be taken when using lasers.

  1. Don't look directly at the laser beam.
  2. Direct the laser beam away from people.
  3. Turn the laser off when not in use.

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