1. 1
   A hospital radiographer uses a particular type of electromagnetic wave to take an image of a patient's broken bone, since these waves can pass through soft tissue but are absorbed more strongly by dense bone.

   (a)

   Which region of the electromagnetic spectrum is being used for this medical scan?

   [1 mark]

   • AX-rays
   • BRadio waves
   • CInfrared
   • DVisible light

   (b)

   Which statement correctly compares the speed of X-rays with the speed of radio waves, both travelling through the vacuum of space?

   [1 mark]

   • AX-rays travel much faster than radio waves in a vacuum
   • BX-rays and radio waves travel at exactly the same speed in a vacuum
   • CRadio waves travel much faster than X-rays in a vacuum
   • DNeither X-rays nor radio waves can travel through a vacuum

   (c)

   State one harmful effect on the human body of excessive exposure to X-rays, and explain why the radiographer stands behind a protective lead screen while operating the X-ray machine.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A satellite television company transmits signals from a broadcasting station on Earth to a satellite in geostationary orbit, and from there back down to individual household dishes.

   (a)

   Which region of the electromagnetic spectrum is typically used for this satellite television transmission?

   [1 mark]

   • AUltraviolet
   • BGamma rays
   • CMicrowaves
   • DVisible light

   (b)

   The company's engineers explain that the television picture and sound information are now sent as a digital signal rather than as an older-style analogue signal. Which of the following is a stated benefit of using a digital signal rather than an analogue signal for this transmission?

   [1 mark]

   • ADigital signals do not require a satellite to be transmitted at all
   • BDigital signals cannot be transmitted using electromagnetic waves at all
   • CDigital signals travel more slowly than analogue signals through the atmosphere
   • DDigital signals allow an increased rate of data transmission and increased range due to accurate signal regeneration

   (c)

   Explain the difference between a digital signal and an analogue signal, and explain how digital signal regeneration allows a signal to travel a greater range without degrading in quality compared with an analogue signal.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A food processing factory uses two different applications of electromagnetic radiation in its production line: infrared lamps to grill food quickly, and gamma radiation to sterilise packaged food to extend its shelf life without heating it significantly.

   (a)

   (a) Explain why infrared radiation is well suited to quickly heating and grilling the surface of food.

   [3 marks]

   (b)

   Explain fully why gamma radiation, rather than infrared radiation, is chosen to sterilise the packaged food, referring to the ability of gamma radiation to kill harmful microorganisms and the importance of not significantly heating the food during this process, and explain a safety precaution the factory must take when using gamma radiation.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A university physics department owns a full set of sources and detectors covering every major region of the electromagnetic spectrum, from radio waves to gamma rays, and challenges students to arrange them correctly in order and describe their uses.

   (a)

   Explain fully the order of the main regions of the electromagnetic spectrum from lowest to highest frequency, and describe at least one typical use for three different regions of your choice, explaining how the properties of each region (in terms of energy and penetration/absorption) make it suitable for the use you describe.

   [6 marks]

   (b)

   One student in the department proposes an experiment: exposing a group of laboratory cell samples separately to controlled, low doses of microwaves, infrared, ultraviolet and X-rays, in order to compare the harmful biological effects of each. Explain fully, referring to the differing amounts of energy carried by each of these four regions of the electromagnetic spectrum, why the potential harmful effects on the living cells would be expected to differ considerably between the four types of radiation, describing at least one specific harmful effect associated with two of these regions.

   [6 marks]

   Total for question 4: 12 marks

End of questions