Chapter 14 Electromagnetic Waves

Question 1

List the seven components of the electromagnetic spectrum in terms of INCREASING WAVELENGTH.

Answer 1

Gamma rays
X-rays
Ultraviolet rays
Visible light
Infrared
Microwaves 
Radio waves.

(Good Xylophones Use Very Interesting Musical Rhythms.)

Question 2

List the seven components of the electromagnetic spectrum in terms of INCREASING FREQUENCY.

Answer 2

Radio waves
Microwaves
Infrared
Visible light
Ultraviolet rays
X-rays
Gamma rays

(Reverse “Good Xylophones Use Very Interesting Musical Rhythms.”)

Question 3

List the 8 common properties of electromagnetic waves.

Answer 3

1. They are transverse waves.
2. They can travel through vacuum because they do not require any medium to travel from one point to another.
3. They transfer energy from one point to another.
4. They travel through vacuum at the same speed of 3.0 x 10^8 m/s, with their respective frequencies and wavelengths.
5. Wave speed equation 𝑣=𝑓𝜆 also applies to EM waves.
6. When travelling from one medium to another, frequency doesn’t change but speed and wavelength can change. (Its frequency only depends on the source of the wave)
7. They obey the laws of refraction and reflection.
8. They carry no electric charge.

Question 4

State the applications of radio waves.

Answer 4

• Radio broadcasting
• Radar
• Telephone transmission

Question 5

State the applications of microwaves.

Answer 5

• Satellite communications
• Microwave ovens
• Global Positioning System (GPS)

Question 6

State the applications of infrared radiation.

Answer 6

• Remote controllers
• Ear thermometers
• Intruder alarms

Question 7

State the applications of ultraviolet radiation.

Answer 7

• Sunbeds (artificial sun-tanning)

- Sterilisation of medical equipment

Question 8

State the applications of x-rays.

Answer 8

• Radiation therapy (used to kill cancer cells)
• Radiography (produce X-ray images for medical diagnosis)
• Airport scanners

Question 9

State the application of gamma rays.

Answer 9

• Radiation therapy (used in cancer treatment; ionizing radiation which can kill living cells)

Question 10

State and explain the effects of electromagnetic waves.

Answer 10

Ionising radiation on living matter:

• Exposure to ionising radiation can damage biological molecules (e.g. proteins and DNA) and lead to abnormal patterns of cell division. This may cause cancers such as leukaemia/ a developing foetus to become deformed.

Infrared heating:

• At barbecues, we feel the heat from the burning charcoal if we are near the barbecue pit. The heat radiating from charcoal is actually infared radiation. We feel warm because our skin and clothes absorb the infrared radiation.