Uses and hazards of electromagnetic waves

Ultraviolet (UV) waves from the Sun travel towards the Earth.

Ultraviolet waves can be grouped by wavelength.

The three groups of wavelengths are UVA, UVB and UVC.

Figure 7 shows, for each group,

• the wavelength range

• the effect of the Earth’s atmosphere on each type of UV wave.

Explain why UVC is potentially the most dangerous ultraviolet radiation but does not cause harm to people.

The speed of electromagnetic radiation is 3 00. 10⁸ m/s.

Calculate the frequency of the shortest wavelength of UVB radiation.

UV radiation of wavelength 365 nm is used to detect forged banknotes.

In a genuine banknote there are marks that cannot be seen using visible light. These marks can be seen using UV radiation.

Explain why the marks can be seen when the UV radiation shines on the banknote.

Your answer should refer to the energy of electrons in atoms.

You may draw a diagram to help with your answer.

This question is about waves in the electromagnetic (e-m) spectrum.

Figure 1 shows some types of radiation that form part of the e-m spectrum and some uses of e-m radiation.

Draw one straight line from each type of e-m radiation to its use.

One line has been drawn for you.

Which of these waves has the highest frequency?

X-rays are also part of the e-m spectrum.

Figure 2 shows an airport security scanner using X-rays to scan passengers’ bags.

Explain why X-rays are used to scan passengers’ bags.

Explain why passengers are not scanned with X-rays.

Figure 1 shows how the visible spectrum of white light is shown on a screen.

Which of these is the best piece of equipment to produce the white light?

Which colour is seen between yellow and blue in the spectrum on the screen?

Figure 2 shows the main parts of the electromagnetic spectrum.

Complete the following sentences using information from Figure 2. Each part of the electromagnetic spectrum may be used once, more than once or not at all.

The part of the electromagnetic spectrum used to detect broken bones is

The part of the electromagnetic spectrum used in thermal imaging is

The part of the electromagnetic spectrum that

• is used to cook food

AND

• has a shorter wavelength than microwaves is

The part of the electromagnetic spectrum that

• is used to sterilise medical equipment

AND

• has a shorter wavelength than x‑rays is

This question is about waves in the electromagnetic (e.m.) spectrum.

The potential danger associated with the waves of the e.m. spectrum increases as

A microwave oven uses waves of frequency 2.45 GHz.

Calculate the wavelength of the microwaves.

The microwave oven is 55% efficient and transfers 42 000 J of energy to some food when it is heated.

Calculate the total amount of energy that must be supplied to the oven.

*(c) X-rays and radio waves are part of the electromagnetic spectrum and have different uses.

These radiations are produced in different ways.

X-rays are emitted when electrons within an atom go through energy changes.

Radiowaves are produced by electrons in circuits.

Compare X-rays with radio waves.

Your answer should refer to

• the uses of both types of radiation

• the different ways that electrons are involved in producing X-rays and radio waves.

Figure 1 shows the parts of the electromagnetic spectrum.

Which row of the table names the parts J, K and L of the electromagnetic spectrum?

All electromagnetic waves can travel in a vacuum.

Which of these is the same for all electromagnetic waves travelling in a vacuum?

X-rays can be useful and harmful to humans.

State one way that x-rays are useful to humans.

State one way that x-rays are harmful to humans.

A person warms their hands in front of a hot fire as shown in Figure 2.

Use words from the box to complete the following sentences.

chemical infrared radio thermal ultraviolet

The electromagnetic waves that the fire mostly emits are_........ waves.

These waves transfer_........ energy to the hands.

Draw one line from each use of wave to the matching electromagnetic wave.

One line has been drawn for you.

Ultraviolet light has a higher frequency than infrared light.

Which of these colours of visible light has the highest frequency?

Figure 1 shows how the brightness of a source of light changes with wavelength.

Describe how the brightness changes with wavelength.

Which colour of visible light has the longest wavelength?

Some television remote controls use infrared radiation and other remote controls use radio waves.

Explain why an infrared remote control may not switch on the television from behind an armchair but a radio wave remote control always will.

Figure 2 is a diagram of a water wave.

A cork is floating on the water.

Use the scale on the diagram to measure the wavelength of the wave.

Describe the motion of the cork.

You should include how the cork moves relative to the direction of travel of the wave.

A different water wave has a wavelength of 0.25 m and a frequency of 1.5 Hz.

Calculate the wave speed.

Figure 7 shows a tuning fork.

When the prongs of the tuning fork are struck, the prongs vibrate in the directions shown by the arrows on Figure 7.

Describe how the vibrating tuning fork causes a sound wave to travel through the air.

You may add to the diagram if it helps your answer.

The following descriptions describe waves from different parts of the electromagnetic spectrum.

Complete each description by adding the name of the wave.

Use the name of each wave only once. Each description refers to a different part of the electromagnetic spectrum.

Description 1

used in cooking

used in short-range communication

typical wavelength 900 nm

Description 2

used in cooking

used in communication

typical wavelength 150 mm

Description 3

used in communication

produced by oscillations in electrical circuits

typical wavelength 150 m

Description 4

used in medical scanning

is emitted by the nucleus of an atom

typical wavelength 2.0 × 10⁻³ nm

When white light crosses the boundary between air and glass, it can split up into the colours of the spectrum.

Explain, in terms of speed, why the light behaves like this.