Question

Gamma rays

D

C

Visible light

B

A

The above table shows different parts of the electromagnetic spectrum.
(a)    Identify the parts of the spectrum marked as A, B, C and D.
(b)    Which of the radiations A or B has the higher frequency?
(c)    State two properties which are common to all parts of the electromagnetic spectrum.
(d)    Name one source of each of the radiation of electromagnetic spectrum.
(e)    Name one detector for each of the radiation.
(f)    Name one use of each of the radiation.

Answer 1

(a) A, B, C and D are microwaves, infrared waves, ultraviolet light and x-rays respectively.
(b) Radiations B (microwaves) have a higher frequency.
(c) Common properties of e-m spectrum:
(i) All electromagnetic waves travel with the same speed in vacuum (or air) which is equal to the speed of light i.e. 3 x 10⁸ m/s.
(ii) These waves are unaffected by the electric and magnetic fields.

(d)

Name of wave	Source
1. Gamma rays	1. cosmic rays
2. X rays	2. When highly energetic electrons are stopped by a heavy metal target of high melting point (x-ray tube)
3. Ultraviolet	3. Sunlight
4. visible light	4. White hot bodies
5. Infrared waves	5. Lamp with thoriated filament.
6. Microwaves	6. Electronic devices such as klystron tube.
7. Radio waves	7. Radio transmissions.

(e) 

Name of waves	Detector
1. Gamma rays	1. Geiger tube
2. X rays	2. Photographic film coated with zinc sulphide.
3. Ultraviolet	3. Photographic plate
4. visible light	4. Eye photo cells
5. Infrared waves	5. Thermopile
6. Microwaves	6. Wave guide tubes
7. Radio waves	7. Earphone

(f)

Name of waves	Use
1. Gamma rays	1. Detecting flaws in metal casting.
2. X rays	2. Diffraction to find crystal structure
3. Ultraviolet	3. Burglar alarms
4. visible light	4. Photography
5. Infrared waves	5. Infra - red photography
6. Microwaves	6. Microwave cooking
7. Radio waves	7. Communication and navigation.