Lesson 3

How is being inside a microwave oven like standing in a city street?

These places are bathed in electromagnetic radiation (the

oven in microwaves, the street in radio waves from TV and radio stations, microwaves from mobile phones, UV from the Sun etc).

How is being inside a microwave oven like standing in a city street?

Lesson 3

Hot Stuff

You will be successful if you can:

• Describe how E-M radiation transfers energy

• Explain ionisation

• Explain how E-M radiation can cause damage to living tissue.

At one end of the electromagnetic spectrum are radio radiations. Radio photons carry little energy.

radio VHF (radio)

radio VLF

radio UHF (TV)

radio (AM radio)

Some types of

electromagnetic

radiation, if

intense enough,

have a

noticeable

warming effect.

Microwave radiation can be good at heating anything with water in it.

Electromagnetic waves transfers energy from source to absorber, and often the only effect is heating of the absorber.

Gamma rays, X-rays, and UV are radiations that have the most energetic photons.

UV

X-ray

gamma rays

Radiation is emitted and absorbed as photons. UV transfers energy to skin, but heating is not the only effect

All types of electromagnetic radiation travel as photons. They are packets of energy.

absorbing molecule

from source

Ionization happens when a photon with enough energy

hits an atom or molecule inside a material.

An individual collision between a photon and an atom can ionize the atom, if the photon is sufficiently energetic

UV radiation, X-rays, and gamma rays transfer energy to material in local and dramatic ways.

IonisationWhen radiation collides with neutral atoms or molecules it alters their structure by knocking off electrons. This will leave behind IONS – this is called IONISING RADIATION.

High energy radiation

Electron

IonisationSome types of radiation are dangerous because they “ionises” atoms – in other words, it turns them into ions by “knocking off” electrons:

Ionisation causes cells in living tissue to mutate, usually causing cancer. High doses can destroy cells completely, causing radiation sickness.

Radiation

Only radiations with high-energy photons can cause ionization.

radio VLF

radio VHF (radio)

microwave

infrared

UV

X-ray

gamma rayscosmic rays

radio UHF (TV)

radio (AM radio)

ionizing radiation

non-ionizing radiation

visible spectrum

Ionisation to you

• Summarise ionisation in a sentence

• How could you improve the ionisation role play we did last lesson?