GCSE Physics - EM Spectrum Mid-Topic Test

What does visible light range from?

From 700nm at the red end to 400nm at the violet end

What are the uses of visible light?

• photography

• medical endoscopy

• sight

What are the risks of visible light?

It can cause burns when it is at a high intensity like lasers.

What do all objects radiate?

All objects radiate out infrared radiation as it is a type of heat transfer.

What are the uses of infrared?

Remote controls - used to change TV channels

Grilling - infrared gives out thermal radiation to cook food

Thermal imaging camera - these pick up the infrared radiation emitted by objects

What are the risks of infrared?

Infrared radiation can transfer enough energy to cause skin burns

What are the wavelengths of microwaves measured in and why?

In centimetres to metres because they have a longer wavelength.

What are the uses of microwaves?

Microwave ovens, mobile phones and GPS (global positioning system)

How do microwave ovens work?

They send out microwaves at high intensities where the light energy is converted into kinetic energy. The water molecules in the food then absorb the microwave radiation (causing them to rotate), and hence gain heat energy and cook the food

How do mobile phones use microwaves?

Microwaves are sent out by a transmitter(the phone) to the nearest base station. The signal is then retransmitted as microwaves to the phone where it is needed.

How does GPS work?

Microwaves can pass through the atmosphere to satellites to find the location of the receiver.

What are the risks of microwaves?

In high dosages, microwaves can cause internal heating of body cells

What are the uses of radio waves?

Terrestrial radio - radio waves bounce off the ionosphere and travel long distances around the Earth

MRI(magnetic resonance imaging) - uses radio frequency waves to generate images of the human body

Why do radio waves have a low risk?

Because they have a low frequency

What are the uses of ultraviolet?

Security marks

Sterilising water - UV can kill bacteria in water

How is ultraviolet used in security marks?

Special pen marking can be used; UV light is absorbed by the ink which emits it as visible light, causing it to fluoresce

What are the risks of ultraviolet?

UV can be ionising so it can cause cellular damage. Exposure to UV can also cause burns

What do x-rays pass and not pass through?

X-rays mostly pass through soft tissue, but do not easily pass through metal or bone.

What are the uses of x-rays?

X-ray images - images areas of our bodies, like bone which allow fewer x-rays through and appear lighter on images

Crack detection - used in industry to check metal parts for cracks

CAT Scans - Computerised axial tomography - generates a 3D image of patient

What are gamma rays?

They are very high energy waves with a very short wavelength and very high frequency

What are the uses of gamma rays?

Treating cancer - gamma can kill some types of cancerous cells better than healthy tissue. This is known as radiotherapy

Sterilising medical equipment - gamma rays kill bacteria

What is the danger of ionising radiation?

If atoms in our cells are ionised, the cells can be damaged and mutated. And if DNA is ionised, it can possibly mutate and cause a tumour to grow.

What is ionising?

When nuclear radiation knocks electrons out of atoms and causes the cells to become charged.

What EM waves are used for communication?

Radio waves and microwaves

What is the spectrum of radio waves and microwaves split into?

Divided into bands of different frequencies

What does the frequency and wavelength affect in communication waves?

• how much information a wave carries

• how far they can travel

• how far they spread out and disperse

What communication are microwaves used for and why?

They are used for satellite communication because they have a smaller wavelength and can get through our atmosphere into space with their higher energy and frequency.

Does the microwave signal weaken?

No because they have smaller wavelengths so spread out less, causing the signal to not weaken.

What is mid-range radio?

Radio waves with a smaller wavelength than a metre are used for terrestrial TV signals. This is because radio waves carry much less info than shorter wavelength microwaves.

What are radio waves with longer wavelengths used for?

Radio waves with a wavelength larger than 100m are used by national and international radio because they have a much longer range

How are electromagnetic waves produced?

They are produced by accelerating charged particles (electrons and protons)

How are radio waves produced?

By oscillating electrons in aerials due to an alternating electrical current

How are microwaves produced?

By rotating atoms due to alternating currents

How is infrared radiation produced?

By vibrating atoms which transfers more thermal energy

How is visible light produced?

Emitted over 800 degrees Celsius when electron drop energy level

How is ultraviolet produced?

Emitted over 1500 degrees Celsius when electron drop energy level

How are X-rays produced?

Caused by the collision of high energy electrons with a metal target

How are gamma rays produced?

By radioactive decay of unstable atomic nuclei. The nuclear decay accelerate the particles

What are changes in atoms and nuclei caused by?

They are caused by the absorption or emission of electromagnetic radiation.