(a) Ultrasound is a sound wave with a frequency above the upper limit of human hearing. What is the maximum frequency that a person can hear? (1 mark)
(b) What type of wave
are X-rays? (1 mark)
(c) Both X-rays and
ultrasound are used by doctors to help diagnose illness.
(i) Explain why, before having an X-ray taken,
all metal jewellery should be removed. (2 marks)
(ii) Explain why having an X-ray taken is
potentially more dangerous than having an ultrasound scan. (2 marks)
(iii) State one advantage of using X-rays to produce
an image of part of the human body rather than ultrasound. (1 mark)
(d) A CT scanner uses
X-rays to produce detailed images of the human body. The table shows the
additional amount of radiation that you are exposed to when having a certain CT
scan.
|
Area of investigation
|
Additional radiation dose (in arbitrary units)
|
|
Abdomen and pelvis
|
800
|
|
Spine
|
600
|
|
Head
|
200
|
(i) About 1 in every 4 people develops cancer
from natural causes. The additional chance of developing cancer from a CT scan
of the head is about 1 in 10 000.
What is
the additional chance of developing cancer from a CT scan of the abdomen and
pelvis? (2 marks)
(ii) Explain why CT scans are taken even though
they increase the chance of developing cancer. (2 marks)
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