Physics 9702 · AS & A Level · The diffraction grating

The diffraction grating — practice question

A parallel beam of light with wavelength $600\,\text{nm}$ is incident at right angles onto a diffraction grating. The separation between neighbouring slits in the grating is $2.0 \times 10^{-6}\,\text{m}$. A screen is set up parallel to the grating, $1.50\,\text{m}$ away from it. Third-order diffraction maxima appear at the two edges of the screen, as shown. What is the separation between the two ends of the screen?

  • A$1.4\,\text{m}$
  • B$2.7\,\text{m}$
  • C$3.1\,\text{m}$
  • D$6.2\,\text{m}$

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