1. 1
   A marine engineer uses a wave tank to model ripples on the surface of water, generating waves with a signal generator connected to a small paddle. The paddle produces ripples with a wavelength of 0.02 m and a frequency of 5 Hz.

   (a)

   Which type of wave are water ripples, in terms of the direction of oscillation compared to the direction of energy transfer?

   [1 mark]

   • ATransverse
   • BLongitudinal
   • CNeither transverse nor longitudinal
   • DBoth transverse and longitudinal

   (b)

   Which equation correctly relates the period T of the ripples to their frequency f?

   [1 mark]

   • AT = f
   • BT = 1/f
   • CT = v/f
   • DT = fλ

   (c)

   Calculate the speed of the ripples produced by the paddle.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A jeweller shines a beam of light into a diamond gemstone. Light entering one face of the diamond travels through the gem and strikes the inside of another face at an angle greater than the diamond's critical angle, before continuing through the stone.

   (a)

   What happens to the light ray when it strikes the internal face of the diamond at an angle greater than the critical angle?

   [1 mark]

   • AIt refracts out of the diamond, bending away from the normal
   • BIt is absorbed completely by the diamond
   • CIt is totally internally reflected
   • DIt splits into two separate rays travelling at the same angle

   (b)

   Which condition must be met for total internal reflection to occur at a boundary?

   [1 mark]

   • AAngle of incidence is less than the critical angle
   • BThe second medium must be optically denser than the first
   • CThe light must be travelling from air directly into glass
   • DAngle of incidence is greater than the critical angle, travelling from a denser into a less dense medium

   (c)

   Explain what happens to the speed and direction of a light ray as it passes from air into the diamond at an angle to the normal (refraction), rather than being totally internally reflected.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A construction engineer uses a portable device that sends a burst of ultrasound down through the ground to check the depth of a buried pipe. The ultrasound pulse has a frequency of 40000 Hz and a wavelength of 0.0875 m as it travels through the soil. The pulse reflects off the pipe and returns to the surface 0.008 s after being sent.

   (a)

   Calculate the speed of the ultrasound wave as it travels through the soil.

   [3 marks]

   (b)

   Using the speed of ultrasound in the soil, calculate the depth of the buried pipe below the surface, given that the pulse takes 0.008 s to travel down to the pipe and back to the surface.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An airport security team uses two different parts of the electromagnetic spectrum: a millimetre-wave body scanner to check passengers for hidden items, and an infrared camera to monitor the skin temperature of arriving passengers for signs of illness.

   (a)

   Explain, in terms of wavelength and frequency, where the waves used in the millimetre-wave body scanner and the infrared camera each sit in the electromagnetic spectrum relative to visible light. Explain one way in which these waves are different from X-rays or gamma rays in terms of their effect on human tissue, and why this makes them suitable for scanning passengers repeatedly.

   [6 marks]

   (b)

   Evaluate the use of infrared cameras, rather than physical contact thermometers, to monitor the body temperature of large numbers of arriving passengers. Include one advantage and one limitation of this method, and explain how an infrared camera is able to detect a passenger's temperature without touching them.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A window manufacturer tests a new type of glass coating. In one experiment, they shine radio waves at the glass and find they pass straight through; in another, they shine ultraviolet light at the coated glass and find that most of it is reflected or absorbed rather than transmitted.

   (a)

   Which statement best explains why the glass coating behaves differently for radio waves and ultraviolet light?

   [1 mark]

   • ADifferent substances absorb, transmit or reflect electromagnetic waves in ways that vary with wavelength
   • BRadio waves and ultraviolet light travel at different speeds through a vacuum
   • CUltraviolet light is a longitudinal wave while radio waves are transverse
   • DGlass can only interact with visible light

   (b)

   Which hazard is most associated with ultraviolet radiation reaching human skin?

   [1 mark]

   • AGene mutation from ionising radiation, with no effect on skin
   • BSkin ageing and skin cancer
   • CBone fractures
   • DHearing damage

   (c)

   Explain why coating glass to reflect ultraviolet radiation, while still allowing radio waves and visible light through, could be useful in a building's windows.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   An optician tests a convex lens of focal length 0.2 m by using it to focus parallel rays of sunlight onto a small piece of paper placed at the lens's principal focus, causing the paper to begin to smoke.

   (a)

   What happens to parallel rays of light passing through a convex lens?

   [1 mark]

   • AThey spread out after passing through the lens
   • BThey remain exactly parallel after the lens
   • CThey are brought to a focus at the principal focus
   • DThey are all absorbed by the lens

   (b)

   Which type of image does a concave lens always produce?

   [1 mark]

   • AReal
   • BInverted and real
   • CMagnified and real
   • DVirtual

   (c)

   The paper is placed exactly at the lens's principal focus. State what this tells you about the focal length of the lens, and explain, in terms of light rays, why the paper heats up at this point.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A student investigates the emission of infrared radiation from four identical containers of hot water with different outer surfaces - matt black, shiny black, matt white and shiny silver - all starting at the same temperature. An infrared detector is placed the same distance from each surface in turn, and the containers are then left to cool in a room kept at a constant, lower temperature.

   (a)

   State which surface would be expected to emit the most infrared radiation in a given time, and explain why, using the idea of a perfect black body.

   [3 marks]

   (b)

   All four containers start at the same temperature and are left to cool in a room at a constant, lower temperature. Explain, in terms of rates of absorption and emission of radiation, why each container's temperature eventually stops falling and becomes constant, equal to room temperature.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A team of geophysicists studies seismic waves generated by an earthquake to learn about the structure of the Earth's interior. Seismic P-waves are longitudinal waves and S-waves are transverse waves; both types travel out from the earthquake's source through the Earth's interior, and detectors are placed at monitoring stations around the world.

   (a)

   Explain the difference between longitudinal and transverse waves using P-waves and S-waves as examples, and explain why only P-waves are detected on the opposite side of the Earth from an earthquake, while S-waves are not.

   [6 marks]

   (b)

   Geophysicists also use the time it takes for P-waves to arrive at different detector stations around the world to work out the structure and size of the Earth's core. Explain, using the idea of wave speed changing at a boundary between different materials, how a sudden change in the time it takes P-waves to arrive at distant detectors can reveal the boundary between the Earth's mantle and its core, and suggest one reason why this method gives only an estimate of the core's size, rather than an exact value.

   [6 marks]

   Total for question 8: 12 marks

End of questions