Diffraction gratingsEdexcel International A Level Physics: Subtopic test

1. 1
   A student shines a red laser beam of wavelength 633 nm at normal incidence on a diffraction grating that has 300 lines per millimetre. A series of bright spots, called maxima, is formed on a distant screen.

   (a)

   What is the spacing d between adjacent slits in the grating?

   [1 mark]

   • A3.3 × 10⁻³ m
   • B3.3 × 10⁻⁶ m
   • C3.0 × 10⁵ m
   • D3.3 × 10⁻⁹ m

   (b)

   What is the angle between the central maximum and the first-order maximum?

   [1 mark]

   • A0.19°
   • B79°
   • C22°
   • D11°

   (c)

   Calculate the highest order of maximum that can be seen on the screen.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   White light containing wavelengths from 400 nm (violet) to 700 nm (red) is directed at normal incidence at a diffraction grating with slit spacing 2.00 × 10⁻⁶ m. The light is then observed on a screen a long way from the grating.

   (a)

   Which colour is diffracted through the largest angle in the first-order spectrum?

   [1 mark]

   • AViolet
   • BBlue
   • CRed
   • DAll colours appear at the same angle

   (b)

   What is the angle of the first-order maximum for violet light of wavelength 400 nm?

   [1 mark]

   • A12°
   • B24°
   • C78°
   • D0.20°

   (c)

   Calculate the angular separation between the first-order maxima for red light of wavelength 700 nm and violet light of wavelength 400 nm.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In Core Practical 6 a student determines the wavelength of light from a laser. She uses a diffraction grating with 600 lines per millimetre at normal incidence, and places a screen 2.50 m from the grating. The first-order maximum is found 1.06 m from the central maximum on the screen.

   (a)

   Describe how the student should set up the apparatus and take measurements so that she can calculate the wavelength accurately.

   [3 marks]

   (b)

   Calculate the wavelength of the laser light.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A technician has two diffraction gratings. Grating X has 200 lines per millimetre and grating Y has 500 lines per millimetre. She uses each in turn with a green laser of wavelength 532 nm at normal incidence.

   (a)

   Calculate the angle of the first-order maximum for each grating, and the highest order that can be seen with each. Explain how the patterns on the screen differ.

   [6 marks]

   (b)

   The technician now uses white light with grating Y. Describe and explain what is seen on the screen, and show by calculation whether the second-order spectrum overlaps the third-order spectrum.

   [6 marks]

   Total for question 4: 12 marks

End of questions