1. 1
   A kitchen has two kettles containing hot water: one has a shiny, polished silver surface, and the other has a matt black surface.

   (a)

   Which kettle emits infrared radiation at the faster rate from its surface?

   [1 mark]

   • AThe shiny silver kettle, because shiny surfaces are the best emitters
   • BThe matt black kettle, because dark, matt surfaces are better emitters than light, shiny surfaces
   • CBoth kettles emit infrared radiation at exactly the same rate regardless of surface
   • DNeither kettle emits infrared radiation because they are not hot enough to glow

   (b)

   The infrared radiation emitted by both kettles is part of the electromagnetic spectrum. What type of wave are all electromagnetic waves, including infrared?

   [1 mark]

   • ATransverse waves
   • BLongitudinal waves
   • CWaves that require a medium to travel through
   • DWaves that cannot travel through a vacuum

   (c)

   Explain why the water in the shiny silver kettle is likely to stay hot for longer than the water in the matt black kettle, if both are left standing at room temperature.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hospital radiographer takes an X-ray image of a patient's broken arm to check how the bone has healed.

   (a)

   Compared with visible light, X-rays have...

   [1 mark]

   • AA longer wavelength and lower frequency
   • BExactly the same wavelength and frequency
   • CA shorter wavelength and higher frequency
   • DNo wavelength or frequency at all

   (b)

   Because of the potential hazards of X-rays, the radiographer stands behind a protective screen while taking the image. Which of the following is a hazard associated with exposure to X-rays?

   [1 mark]

   • ASkin cancer caused only by prolonged sunlight exposure
   • BA drop in body temperature
   • CPermanent hearing damage
   • DDamage to cells due to their ionising effect

   (c)

   Explain why the bone appears clearly as a distinct white shape on the X-ray image, while the soft tissue around it barely appears at all.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A local radio station broadcasts music using radio waves from a tall transmitter mast, while a nearby security company uses invisible ultraviolet marking pens to write serial numbers on valuable equipment, which can only be read under a UV lamp.

   (a)

   Describe why radio waves are a suitable part of the electromagnetic spectrum for broadcasting music over long distances.

   [3 marks]

   (b)

   Explain how the ultraviolet security marking system works, and describe one hazard of ultraviolet radiation together with a precaution that could reduce exposure to it.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A food processing plant uses gamma rays to sterilise packaged food before it is sent to shops, killing any bacteria present without needing to open the packaging. Meanwhile, a factory worker nearby uses a mobile phone, which sends and receives signals using microwaves.

   (a)

   Explain how gamma rays are used to sterilise the food, and discuss the hazards associated with gamma radiation and how workers at the plant are protected from them.

   [6 marks]

   (b)

   Explain why microwaves are a suitable choice for mobile phone communication, and discuss a hazard associated with microwave radiation and how mobile phone design or usage habits can reduce this risk.

   [6 marks]

   Total for question 4: 12 marks

End of questions