Question 1
A point source produces circular water wavefronts in a ripple tank.
Define a wavefront.
[1]
State the direction of the rays for these circular wavefronts.
[1]
State what the spacing between adjacent wavefronts represents.
[1]
Question 2
A student observes water waves passing through a narrow gap.
Describe the change in shape of the wavefronts after the gap when the gap width is similar to the wavelength.
[2]
State one quantity of the waves that remains unchanged after diffraction in the same medium.
[1]
Question 3
Plane water waves travel from deep water into shallow water at an angle to the boundary.
State what happens to the frequency at the boundary.
[1]
Explain why the wavelength changes.
[2]
Question 4
A light ray travels from air into a plastic block of refractive index 1.40. The angle of incidence is .
Calculate the angle of refraction.
[2]
State whether the ray bends towards or away from the normal.
[1]
Question 5
Two wave pulses travel towards each other along a stretched rope.
State the principle of superposition.
[1]
Explain what happens when two equal pulses, one upward and one downward, completely overlap.
[2]
Question 6
Two coherent loudspeakers emit in phase with wavelength . A microphone is placed where the path difference from the speakers is .
Determine whether the interference is constructive or destructive.
[2]
State one reason why equal path-difference conditions may not produce complete silence at a minimum.
[1]
State why the sources must be coherent for a stable pattern.
[1]
Question 7
Monochromatic light of wavelength is incident normally on a single slit of width .
Calculate the angle to the first minimum.
[2]
State the angular width of the central maximum.
[1]
Question 8
A single-slit diffraction pattern is observed on a screen. The slit width is then decreased while the incident monochromatic light is unchanged.
Describe the change in width of the central maximum.
[1]
Describe the change in intensity of the pattern.
[1]
Explain the change in width using the diffraction equation.
[1]
Question 9
A diffraction grating has . Light of wavelength is incident normally.
Determine the grating spacing.
[1]
Calculate the angle of the first-order maximum.
[2]
Question 10
White light is incident normally on a diffraction grating.
State the colour of the zero-order maximum.
[1]
Compare the angles of the red and violet first-order maxima.
[1]
Explain the comparison in (b).
[1]
Question 11
Light in a glass block has a critical angle of at a glass-air boundary.
Define critical angle.
[2]
Determine the refractive index of the glass.
[2]
Question 12
In a Young double-slit experiment, the distance between the slits and screen is 1.80 m. The slit separation is 0.300 mm. The distance across 10 adjacent fringe spacings is 30.0 mm.
Determine the fringe separation.
[1]
Calculate the wavelength of the light.
[2]
Suggest why measuring across 10 fringe spacings improves the result.
[1]
Question 13
A rectangular slit is illuminated by monochromatic light.
State where the first diffraction minimum occurs in terms of wavelength and slit width .
[1]
Explain, using superposition, why a minimum is produced in this direction.
[3]
Question 14
A real double slit has slit separation and slit width .
State which quantity mainly determines the separation of the fine interference fringes.
[1]
State which quantity mainly determines the width of the diffraction envelope.
[1]
Explain what is meant by a missing order in this pattern.
[2]
Question 15
A monochromatic beam illuminates a grating with many equally spaced slits. A second grating has the same slit spacing but more illuminated slits.
State what happens to the angular positions of the principal maxima.
[1]
Explain what happens to the intensity of a principal maximum.
[2]
Question 16
A diffraction grating has spacing . Light of wavelength 500 nm is incident normally.
Determine the maximum possible order.
[2]
Explain why no higher order is observed.
[1]
State what would happen to the maximum order if the wavelength were increased.
[1]
Question 17
A ray of light is directed inside a glass optical fibre surrounded by air.
Define total internal reflection and state the two conditions required for it to occur.
[3]
Explain how total internal reflection allows light to be guided along the fibre, including the role of the critical angle.
[3]
Question 18
A student uses a laser and double slit to determine the wavelength of light.
Outline how the fringe separation should be measured to reduce uncertainty.
[2]
Evaluate the method, explaining how the wavelength is determined and discussing two significant sources of uncertainty or error.
[5]
Question 19
Wavefront-ray diagrams can represent both refraction and diffraction.
State two features that all correct wavefront-ray diagrams should show.
[2]
Compare and contrast refraction at a boundary with diffraction through an aperture, referring to wavefront spacing, ray direction and wave speed.
[4]
Question 20
Two-source interference is observed using water waves, sound waves or light.
Define coherence and state the path-difference conditions for constructive and destructive interference for sources initially in phase.
[3]
Discuss why a stable interference pattern is observed only under particular conditions, referring to coherence, overlap and amplitude.
[5]
Question 21
A monochromatic laser beam is incident normally on a single rectangular slit.
Describe the main features of the single-slit diffraction intensity pattern.
[3]
Explain how the first minimum is produced and how changing slit width affects the pattern.
[4]
Question 22
A student uses a diffraction grating to identify wavelengths in a light source.
Derive or state the grating equation for normal incidence and define its symbols.
[3]
Evaluate the use of a diffraction grating for analysing white light and monochromatic light, including the maximum possible order and experimental uncertainties.
[5]
Question 23
A double-slit experiment is performed first with very narrow slits and then with real slits of finite width.
State the formula for the spacing of the double-slit interference fringes and the formula for the first minimum of a single-slit diffraction pattern.
[2]
Compare and contrast the predicted intensity patterns, explaining the modulation of the double-slit pattern by the single-slit envelope.
[5]
Question 24
Multiple-slit interference is used in spectroscopy.
Explain why increasing the number of illuminated slits changes the sharpness and intensity of the principal maxima.
[3]
Discuss how a diffraction grating can separate wavelengths, including white light, maximum order and the role of the finite width of the slits.
[5]
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