Waves and Particle Nature of LightEdexcel International A Level Physics: Topic test

20 questions, 54 marks

Edexcel International A Level Physics

Waves and Particle Nature of Light topic test

Total 54 marks

Name

Class

Date

1
A floating buoy on a lake rises and falls through 12 complete oscillations in 30 s as regular water waves pass it. The wavelength of the waves is 4.0 m.
(a)
What is the frequency of the waves?
[1 mark]
A0.40 Hz
B2.5 Hz
C12 Hz
D0.033 Hz
(b)
What is the speed of the waves?
[1 mark]
A0.10 m s⁻¹
B10 m s⁻¹
C1.6 m s⁻¹
D48 m s⁻¹
(c)
Two points on the same line along the direction of travel of the waves are 1.0 m apart. Calculate the phase difference between the motion of water at the two points.
[2 marks]
Total for question 1: 4 marks
2
A ray of light travels in water of refractive index 1.33 and strikes a flat boundary with a glass plate of refractive index 1.52 at an angle of incidence of 35°. The other face of the glass plate is in contact with air. The speed of light in a vacuum is 3.00 × 10⁸ m s⁻¹.
(a)
What is the angle of refraction in the glass?
[1 mark]
A35°
B30°
C41°
D22°
(b)
What is the speed of light in the glass?
[1 mark]
A2.3 × 10⁸ m s⁻¹
B4.6 × 10⁸ m s⁻¹
C3.0 × 10⁸ m s⁻¹
D2.0 × 10⁸ m s⁻¹
(c)
Calculate the critical angle for light travelling in the glass towards the glass–air boundary.
[2 marks]
Total for question 2: 4 marks
3
A microwave transmitter faces a flat metal plate. A small detector is moved along the line between the transmitter and the plate and finds a series of minimum signals. Adjacent minima are 1.43 cm apart. The speed of microwaves in air is 3.00 × 10⁸ m s⁻¹.
(a)
Explain how the minima and maxima of signal arise.
[3 marks]
(b)
Calculate the frequency of the microwaves.
[4 marks]
Total for question 3: 7 marks
4
A violet laser emits light of wavelength 405 nm. The beam is directed at normal incidence at a diffraction grating with 800 lines per millimetre. The Planck constant is 6.63 × 10⁻³⁴ J s, the speed of light is 3.00 × 10⁸ m s⁻¹ and 1 eV = 1.60 × 10⁻¹⁹ J.
(a)
Calculate the angles to the normal of all the maxima that can be seen on one side of the central maximum, and state the total number of maxima observed.
[6 marks]
(b)
The laser beam is directed at a clean caesium surface (work function 2.1 eV) and then at a clean zinc surface (work function 4.3 eV). A student suggests that photoelectrons could be emitted from the zinc if the intensity of the laser beam were increased enough. Evaluate this suggestion, with calculations.
[6 marks]
Total for question 4: 12 marks
5
A beam of thermal neutrons, each moving at 2.2 × 10³ m s⁻¹, is directed at a thin crystal in which the spacing between atomic planes is about 2 × 10⁻¹⁰ m. The mass of a neutron is 1.67 × 10⁻²⁷ kg and the Planck constant is 6.63 × 10⁻³⁴ J s.
(a)
What is the de Broglie wavelength of the neutrons?
[1 mark]
A1.8 × 10⁻⁷ m
B3.6 × 10⁻¹⁰ m
C1.8 × 10⁻¹⁰ m
D5.5 × 10⁹ m
(b)
Why do the neutrons show noticeable diffraction as they pass through the crystal?
[1 mark]
ATheir wavelength is much larger than the atomic spacing
BTheir wavelength is much smaller than the atomic spacing
CThey are uncharged, so the electrons in the crystal cannot deflect them
DTheir wavelength is comparable to the atomic spacing
(c)
Explain how the pattern produced by the neutrons after passing through the crystal provides evidence for the wave nature of neutrons.
[2 marks]
Total for question 5: 4 marks
6
An atom has three lowest energy levels: n = 1 at −9.0 eV, n = 2 at −4.5 eV and n = 3 at −2.0 eV. The Planck constant is 6.63 × 10⁻³⁴ J s, the speed of light is 3.00 × 10⁸ m s⁻¹ and 1 eV = 1.60 × 10⁻¹⁹ J.
(a)
What is the frequency of the photon emitted when an electron moves from n = 3 to n = 2?
[1 mark]
A6.0 × 10¹⁴ Hz
B1.1 × 10¹⁵ Hz
C1.7 × 10¹⁵ Hz
D3.8 × 10³³ Hz
(b)
A photon of energy 5.0 eV is incident on atoms in the ground state. What happens?
[1 mark]
AThe atoms are excited to n = 2
BThe photon is not absorbed
CThe atoms are ionised
DThe atoms are excited to n = 3
(c)
Calculate the wavelength of the photon emitted when an electron moves directly from n = 3 to n = 1.
[2 marks]
Total for question 6: 4 marks
7
A car parking sensor emits a short pulse of ultrasound of frequency 40 kHz and duration 0.50 ms. The speed of ultrasound in air is 340 m s⁻¹. The sensor detects an echo from a wall 5.9 ms after the pulse is emitted.
(a)
Calculate the distance from the sensor to the wall.
[3 marks]
(b)
Two small objects lie one behind the other along the line of travel of the pulse. Calculate the smallest separation of the objects for which their echoes can be distinguished.
[4 marks]
Total for question 7: 7 marks
8
A small LED lamp radiates light of wavelength 550 nm. The total power radiated as light is 12 W, spread uniformly in all directions, and the lamp can be treated as a point source in air. The Planck constant is 6.63 × 10⁻³⁴ J s and the speed of light is 3.00 × 10⁸ m s⁻¹.
(a)
An observer is 20 m from the lamp. Calculate the number of photons entering the observer's pupil each second, given that the area of the pupil is 4.0 × 10⁻⁵ m².
[6 marks]
(b)
A student claims that if the observer moves to a distance of 40 m, the number of photons entering the pupil each second will halve. Evaluate this claim.
[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).