Chapter 14: Electromagnetic waves

Question 1

State the electromagnetic waves from the longest to shortest wavelengths

Answer 1

Radiowaves, microwaves, infrared radiation, visible light, ultraviolet, X-rays, gamma rays

Question 1

What are some properties of electromagnetic waves? (8)

Answer 1

1. Electromagnetic waves are transverse waves. They comprise of electric and magnetic fields that oscillate at 90 degrees to each other
2. They can travel through vacuum
3. They transfer energy from one place to another
4. They travel at the same of speed of 3.0x108/s in a vacuum
5. The wave speed equation, v=fx (v=wave speed, f=frequency of the wave, x=wavelength of the wave)
6. When an electromagnetic wave travels from one medium to another, its speed and wavelength changes, but its frequency does not change
7. They obey the laws of reflection and refraction
8. they carry no electric charge

Question 2

What are applications of electromagnetic waves?

Answer 2

Radio waves: Over-the-air television and communications
Microwaves: Microwave ovens, satellite television and Global Positioning System
Infrared radiation: Remote controllers, ear thermometers and intruder alarms
Visible light: Optical fibres
Ultraviolet radiation: unbends and sterilisation of equipment
X-rays: Radiation therapy and imaging
Gamma rays: radiation therapy

Question 3

What are effects of electromagnetic waves

Answer 3

1. cause cancers such as leukaemia
2. A developing foetus to become deformed (This is why ultrasound imaging are used)

Question 4

What does “transverse wave” mean?

Answer 4

It means that the direction the waves travel in is perpendicular to the direction of vibrations.

Question 5

Effect of ionising radiation on living matter

Answer 5

Ionising radiation is a radiation that has enough energy to remove electrons from atoms or molecules