Electromagnetic waves

What type of waves are electromagnetic waves?

Transverse

What can all electromagnetic waves do?

• Transfer energy as radiation

• Travel through a vacuum

• Travel at the same speed through a vacuum or air

Order the electromagnetic spectrum from low frequency to high frequency waves

• Radiowaves

• Microwaves

• Infrared

• Visible light

• Ultraviolet

• X-ray

• Gamma rays

Why are radiowaves used for communication?

• They are transmitted easily through the air

• They don't cause damage if absorbed by the human body

• Can be reflected to change direction (2-way communication)

How do microwaves heat up food?

• They have high frequencies

  ↳ absorbed by the molecules in food

• This causes the internal energy of the molecules to increase

• Which increases the temperature of food

How does radio communication work?

• Radio waves produce oscillations

  ↳ absorbed by a conductor → creates an alternating current

• Current has the same frequency as the radiowave

• Information is coded into the wave and then decoded when received

Which electromagnetic waves are dangerous for humans?

• Ultraviolet waves

• X-rays

• Gamma rays

why can infrared rays be used in electrical heaters?

• Have frequencies which are absorbed by some chemical bonds

• Internal energy of the bonds increases when infrared light is absorbed

• So this increases the temperature

How are gamma rays produced?

Changes in a nucleus of an atom → nuclear radiation

Why is ionising radiation bad

They can add or remove electrons from molecules which produces electrically charged ions

↳ causes changes in a cell

Give 2 examples of the hazards of ionising radiation

Ultraviolet waves → Skin aging prematurely, skin cancer

X-rays and gamma rays → Mutation of genes which causes cancer

What happens when electromagnetic waves are generated/absorbed?

Changes take place in atoms or the nuclei of atoms

How do electromagnetic waves transfer energy?

They transfer energy from the source, to an absorber

What can visible light be used for?

Communication using fibre optics (thin pieces of glass) → TV signals

• Pulses of light can be transmitted down optic fibres

• These pulses carry information

Why can visible light carry a lot of information?

It has short wavelengths

What is a use for UV?

Energy-efficient light bulbs

• Short wavelength → carries more energy than visible light

• This energy is absorbed by the lightbulb and converted into visible

• Requires less energy than a normal lightbulb