P13 - Electromagnetic Waves

Question 1

2 properties:

electromagnetic waves

Answer 1

• transverse
• 300,000,000 m/s in a vacuum
• (electrical and magnetic fields)

Question 2

list:

electromagnetic spectrum

(high to low wavelength)

Answer 2

• radio waves
• microwaves
• infrared
• visible light
• ultraviolet
• x-rays
• gamma rays

Question 3

How are radio waves produced?

Answer 3

Oscilliations in electrical circuits (AC)

Hz of AC is same as Hz of wave

Question 4

What happens when radio waves are absorbed?

Answer 4

Induce oscillations in an electrical
circuit (create AC)

with the same Hz as the wave

Question 5

How does ionising radiation cause harm?

Answer 5

They knock off electrons from their shells forming ions. These ions may be inside a cell which causes them to be more reactive. This can cause death of tissue cells, or if in the nucleus, mutations which cause cancerous growths.

Question 6

list:

uses of electromagnetic waves

Answer 6

• radio waves and microwaves – long distance communications
• infrared – heating
• visible light – fibre optic communications
• ultraviolet – tanning
• X-rays and gamma rays – medical imaging and treatments

Question 7

explain:

refraction from air to glass

in terms of wave fronts

Answer 7

1. different parts of the wavefront enter the glass at different times
2. velocity is less in glass
3. so one part of the wave front changes speed before other parts