# Waves - Properties of Waves 01

This GCSE Physics quiz will challenge you on properties of waves. Every day, probably without even thinking about it, all life on Earth uses waves. There are light waves for seeing and sound waves for hearing. Humans have discovered how to use radio waves for communications and microwaves for TV and your mobile phone. You can't see most waves but they are all around you. Some waves that you can see are water waves and you can see and feel the effects of the waves that disturb the Earth during an earthquake.

But what exactly is a wave? A wave is a disturbance in a medium that transfers energy from one place to another. You can really get a feel for this if you have ever seen video clips of earthquakes or tsunamis. These carry huge amounts of energy, sufficient energy to destroy vast areas.

The energy from the epicentre of an earthquake travels outwards as waves, where it reaches the surface. The energy is so great that it can move large chunks of rock and soil through several metres in a few seconds. Tsunamis have so much energy that they can travel for many kilometres inland from the coast, destroying almost everything in their path.

Waves come in two basic types - transverse and longitudinal. Transverse waves vibrate at right angles to the direction in which the energy is travelling whilst longitudinal waves vibrate in the same direction as the energy is travelling. All waves require a medium that allows the vibrations to pass. Longitudinal waves require a material medium (a medium made from matter) in order for them to pass as the energy is transferred by the particles of the medium vibrating backwards and forwards. They travel as a sequence of regular compressions and rarefactions. Longitudinal waves cannot therefore travel through space as it is a vacuum and contains very few particles, certainly not enough to be able to transmit sound. Science fiction films ignore this, you would not in fact hear the engines of a spacecraft, hear any explosions or the sound of guns firing, but that would make the films really boring!

For the GCSE, you need to know some examples of waves of both types and their properties. All sound waves and some earthquake waves are longitudinal. Water waves, light waves and X-rays are all examples of transverse waves. A wave that causes the particles of a substance to vibrate can be referred to as a mechanical wave. Examples of these are all earthquake waves, water waves and ultrasonic waves that are being used to break down kidney stones. Mechanical waves can be transverse or longitudinal.

Electromagnetic waves form a continuous spectrum of related transverse waves that transfer energy from one place to another at the same speed - the speed of light. Their wavelengths vary from about 10-15 metres to more than 104 metres. They are non-mechanical, in other words, they do not require matter in order to be able to transfer energy, so they are therefore the only waves that can travel in a vacuum. The medium that they require is the electric and magnetic fields that extend throughout the known universe. For your GCSE, you need to know the order of these in terms of the energy they carry, their frequencies and wavelengths.

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1. What types of electromagnetic waves can travel through a vacuum?
Any type of electromagnetic wave can travel through the emptiness of a vacuum because it is a disturbance in electric and magnetic fields
2. What type of waves can mechanical waves be?
Good examples of this type of wave are earthquake waves
3. How fast do electromagnetic waves travel in a vacuum?
At GCSE, you can take the speed of light as being 300,000 km per second. Electromagnetic waves could therefore travel round the equator about 12 times in a single second
4. What do waves transfer?
Waves transfer energy from one point to another
5. The size of an electromagnetic wave's wavelength can vary between which range?
The shortest wavelength waves are gamma, the longest are radio. These are also the highest and lowest frequency waves but they travel at the same speed
6. What are the two forms that waves travel in?
These descriptions refer to the way the wave is vibrating (oscillating)
7. What is a transverse wave?
Transverse is a word that means across, perpendicular means 'at right angles to'
8. What type of waves are sound waves?
Sound waves travel as longitudinal waves meaning they require particles to transfer the energy of the wave. This is why in a vacuum sound waves cannot travel
9. What is a longitudinal wave?
As the wave passes, the particles of the medium are alternately compressed and uncompressed. These are referred to as compressions and rarefactions
10. What type of waves are electromagnetic waves?
The shortest wavelength (highest frequency) electromagnetic waves carry higher energies