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CC2404 Applied Physics and Instrumentation in Health Care

Solution of Problems Unit 10 (2009)

1. The electromagnetic spectrum includes radio waves, microwaves, infra-red, visible light,
ultraviolet, X-rays and gamma rays.

a Which statement about electromagnetic waves is correct?

A They all have the same wavelength.
B They all have the same frequency.
C They are all transverse waves. (Correct)
b Name two types of electromagnetic wave used to cook food. (microwaves, infra-red)
c Name one type of electromagnetic wave used to detect a break in a bone. (X-rays)
(London Foundation, June 99)

2. Which of the following types of radiation has

a the longest wavelength, (B radio waves)
b the highest frequency (X-rays)
B radio waves
C light
D X-rays

3. Name one type of electromagnetic radiation which

a causes sun-tan, (UV)

b is used for satellite communication, (radio waves)
c is used to sterilize surgical instruments (UV)
d is used in TV remote control (infra-red)

4. Which of the following is NOT a factor that would affect the amount of UV radiation
reaching the ground?

a. Latitude
b. Altitude
c. Longitude
d. Sun elevation Ans. c

5. What is the possible long-term hazard of UV on human skin?

a. induction of skin cancer
b. reddening of the skin
c. Vitamin D Ans. a

6. Which of the statement concerning the causes of suntan and sunburn is correct?

a. UV-A causes suntan and UV-B causes sunburn

b. UV-A causes sunburn and UV-C causes suntan
c. Both UV-A and UV-B will cause suntan but not sunburn
d. Both UV-A and UV-B will cause sunburn but not suntan Ans. a
7. Decide each of the following statement true or false.
a) A tan results from your body defending itself against further damage from UV radiation. (T)
b) You can’t get sunburnt on a cloudy day. (F)
c) You can’t get sunburnt while in the water. (F)
d) UV radiation exposure is cumulative during the day. (T)

8. A VHF radio station transmits on a frequency of 100 MHz (1 MHz = 106 Hz). If the speed of
radio waves is 3× 108m/s,
a what is the wavelength of the waves,
c 3 ×10 8
λ= = m = 3m
f 10 8
b how long does the transmission take to travel 60km?
60 ×10 3
t= s = 2 ×10 −4 s
3 ×10 8

c. What is its photon energy in J and in eV ?

E = hf = 6.63 ×10 −34 J ⋅ s ×1 ×10 8 / s = 6.63 ×10 −26 J = 4.14 ×10 −7 eV