Refraction, diffraction and interferenceAQA A-Level Physics: Topic test

20 questions, 54 marks

AQA A-Level Physics

Refraction, diffraction and interference topic test

Total 54 marks

Name

Class

Date

1
A ray of light from a lamp passes from air into a block of transparent plastic of refractive index 1.50. Take the speed of light in air as 3.00×10⁸ m s⁻¹.
(a)
What is the speed of light in the plastic?
[1 mark]
A4.50×10⁸ m s⁻¹
B2.00×10⁸ m s⁻¹
C1.50×10⁸ m s⁻¹
D3.00×10⁸ m s⁻¹
(b)
The ray meets the surface at an angle of incidence of 40.0°. What is the angle of refraction in the plastic?
[1 mark]
A26.7°
B60.0°
C74.6°
D25.4°
(c)
Show that the critical angle for a boundary between this plastic and air is about 42°.
[2 marks]
Total for question 1: 4 marks
2
A helium-neon laser emits red light of wavelength 633 nm. The beam is incident normally on a diffraction grating that has 500 lines per millimetre.
(a)
What is the spacing d between adjacent slits of the grating?
[1 mark]
A2.00×10⁻⁶ m
B2.00×10⁻³ m
C5.00×10⁵ m
D2.00×10⁻⁷ m
(b)
What is the highest order of maximum that can be observed?
[1 mark]
A2
B4
C3
D5
(c)
Calculate the angle between the normal and the second-order maximum.
[2 marks]
Total for question 2: 4 marks
3
Monochromatic light from a laser illuminates two narrow parallel slits that are 0.25 mm apart. A screen is placed 2.40 m from the slits and a clear interference pattern is seen. The distance across ten fringe spacings is measured as 58 mm.
(a)
Calculate the wavelength of the light.
[3 marks]
(b)
The laser is replaced by a lamp that emits white light. Describe and explain the appearance of the pattern on the screen.
[4 marks]
Total for question 3: 7 marks
4
An endoscope contains thin step-index glass fibres. Each fibre has a core of refractive index 1.62 surrounded by cladding of refractive index 1.52. The same type of fibre is also used to carry short pulses of infrared light in a short data link.
(a)
Calculate the critical angle at the core–cladding boundary. Explain how light is guided along the fibre and why the cladding is needed.
[6 marks]
(b)
Explain how modal dispersion and material dispersion cause pulses to broaden in the fibre. Explain why pulse broadening limits the rate at which pulses can be sent, and suggest one way of reducing each type of dispersion.
[6 marks]
Total for question 4: 12 marks
5
Microwaves of wavelength 2.8 cm are emitted by a transmitter towards a metal plate that has two narrow slits 7.0 cm apart. A small detector is moved along a line parallel to the plate and 0.50 m from it.
(a)
At one position the detector reads almost zero signal. The path difference from the two slits to this position is 4.2 cm. Which statement best explains the minimum?
[1 mark]
AThe waves arrive in phase, so they superpose to give the maximum amplitude.
BThe waves arrive in phase, but they travel in opposite directions and cancel.
CThe waves are no longer coherent at this position, so no pattern is formed.
DThe waves arrive in antiphase, so their displacements cancel.
(b)
What is the spacing between adjacent maxima along the line of the detector?
[1 mark]
A0.20 m
B1.25 m
C3.9×10⁻³ m
D0.40 m
(c)
Explain why the two slits must be illuminated by the same transmitter for a stable pattern to be observed.
[2 marks]
Total for question 5: 4 marks
6
A ray of light travelling in glass of refractive index 1.55 meets a boundary between the glass and air.
(a)
What is the critical angle for the glass–air boundary?
[1 mark]
A49.8°
B32.8°
C40.2°
D24.6°
(b)
The ray meets the boundary at an angle of incidence of 35.0°. What happens to the ray?
[1 mark]
AIt refracts into air at 22.6° to the normal.
BIt refracts into air at 62.8° to the normal.
CIt refracts into air at 54.3° to the normal.
DIt is totally internally reflected.
(c)
Show that a ray of light meeting the boundary at 45° is totally internally reflected.
[2 marks]
Total for question 6: 4 marks
7
A student determines the wavelength of light from a monochromatic source using a diffraction grating that has 350 lines per millimetre. The light is incident normally on the grating. The student measures the angle between the normal and the second-order maximum as 21.5°.
(a)
Calculate the wavelength of the light.
[3 marks]
(b)
Suggest two ways in which the student could reduce the uncertainty in the value of the wavelength. Explain how each helps.
[4 marks]
Total for question 7: 7 marks
8
A teacher has a red laser diode of wavelength 670 nm, a double slit with slits 0.20 mm apart and a diffraction grating with 100 lines per millimetre. A screen is placed 2.0 m from the double slit or the grating in turn, and the light is incident normally.
(a)
The teacher shines the laser through the double slit and then through the grating. Calculate the fringe spacing for the double slit and the angle of the first-order maximum for the grating. Compare the two patterns that are seen.
[6 marks]
(b)
The laser is replaced by a lamp that emits white light. Describe and explain how the patterns from the double slit and from the grating differ from those seen with the laser, and how they differ from each other.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).