Chapter 14: Electromagnetic Waves

Question 1

Electromagnetic Spectrum (based on wavelength, longest –> shortest)

Answer 1

Radio Waves 
Microwaves 
Infrared 
Visible Light 
Ultraviolet 
X-rays 
Gamma Rays 
(radiowaves hv the lowest frequency) 
(red --> lowest frequency, highest wavelength)

Question 2

Properties of electromagnetic waves

Answer 2

1. transverse waves (comprise electric and magnetic fields that oscillate at 90° to each other)
2. can travel through vacuum
3. transfer energy from one place to another
4. travel at the same speed of 3.0x10^8 ms^-1 in vacuum, with their respective frequencies and wavelengths
5. wave speed equation, v= fλ, is applicable to all EM waves
6. when an EM wave travels from one medium to another (e.g. from air to glass) its
   - speed and wavelength change
   - its frequency does not change
7. obey the laws of reflection and refraction
8. carry no electric charge

Question 3

Radio waves (Applications)

Answer 3

• AM radio (amplitude modulation)
• submarine communication
• FM radio
• over-the-air television (or terrestrial television)

Question 4

Microwaves (application)

Answer 4

• microwave ovens
• satellite televisions
• Global Positioning System (GPS)

Question 5

Infrared radiation (applications)

Answer 5

• remote controllers
• ear thermometers
• intruder alarms

Question 6

Visible light

Answer 6

-optical fibers (medical purposes & telecommunications)

Question 7

Ultraviolet radiation (applications)

Answer 7

• sunbeds (artificial tanning)

- germicidal lamps (sterilise medical and laboratory equipment)

Question 8

X-rays (application)

Answer 8

• radiation therapy

- imaging

Question 9

Gamma rays (application)

Answer 9

-radiation therapy (cancer treatment)

Question 10

Effects of EM waves

Answer 10

-ionising radiation on living matter
•radiation that has enough energy to remove electrons from atoms or molecules, thus creating ions
•exposure can damage biological molecules (e.g. proteins and DNA) –> lead to abnormal patterns of cell division –> may cause: cancers (leukaemia), a developing foetus to become deformed

-infrared heating