1. 1
   A radio station broadcasts music using electromagnetic waves. The signal is transmitted through the air by an aerial and picked up by radios in the local area. The waves have a wavelength of 300 m and travel at the speed of light, 3 x 10^8 m/s.

   (a)

   What type of wave is a radio wave?

   [1 mark]

   • ALongitudinal
   • BTransverse
   • CA sound wave
   • DA wave that requires a medium to travel

   (b)

   Compared with visible light, how do radio waves differ in terms of wavelength and frequency?

   [1 mark]

   • ALonger wavelength and lower frequency
   • BLonger wavelength and higher frequency
   • CShorter wavelength and higher frequency
   • DShorter wavelength and lower frequency

   (c)

   Calculate the frequency of the radio wave broadcast by the station.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An engineer designs a satellite communication system and, separately, a microwave oven; both devices use microwaves for entirely different purposes.

   (a)

   Why are microwaves used to cook food in a microwave oven?

   [1 mark]

   • AThey are reflected by the metal walls of the oven and never reach the food
   • BThey pass straight through the food without any energy transfer
   • CThey are absorbed by water molecules in the food, transferring energy that heats it
   • DThey ionise the atoms in the food to release heat

   (b)

   Which property of microwaves makes them suitable for satellite communication?

   [1 mark]

   • AThey are absorbed completely by the Earth's atmosphere
   • BThey can only travel in straight lines through solid metal
   • CThey travel more slowly than radio waves
   • DThey can be transmitted through the atmosphere to and from orbiting satellites

   (c)

   State two different everyday uses of microwaves and, for each use, give the property of microwaves that makes them suitable.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A hospital radiography department uses X-rays to image a patient's broken bone, and a separate department uses gamma rays to treat a cancerous tumour deep inside the body.

   (a)

   Explain why X-rays are suitable for imaging a patient's broken bone.

   [3 marks]

   (b)

   Explain the hazards that X-rays and gamma rays pose to human body tissue, and describe two precautions taken by hospital staff to reduce their exposure to this radiation.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Scientists studying the Earth's atmosphere are investigating how depletion of the ozone layer affects the amount of ultraviolet radiation reaching the Earth's surface, and the resulting risks to human health.

   (a)

   Describe the electromagnetic spectrum in order of increasing frequency, and explain how the atmosphere, including the ozone layer, absorbs different parts of this spectrum by different amounts.

   [6 marks]

   (b)

   Evaluate the health risks to humans from increased ultraviolet exposure caused by ozone depletion, and discuss why decisions about international action to address this issue involve more than scientific evidence alone.

   [6 marks]

   Total for question 4: 12 marks

End of questions