Now you see it, Now you Don't

...are a regular pattern of disturbance. They transfer energy from one point to another without any transfer of matter. They can be produced in ropes, springs and on the surface of water.

Amplitude- is the maximum vertical disturbance cause by a wave (height)

Wavelength-is the distance between corresponding points on two successive disturbances

Frequency- is the number of waves produced in one second.

Transverse waves- the pattern of disturbance is at right angles (90) to the direction of movement

Longitudinal waves-the pattern of disturbance is in the same direction as the direction of wave movement

All energy originates from the sun Energy travels to the Earth in the form of electromagnetic waves.

These waves form the electromagnetic spectrum in which they are ordered according to their frequency and wavelength.

' Good Xylophones use very interesting musical rhythms '

• Radio waves- transmitting tv programmes between different places
• microwaves- sattilite, mobile phones and cooking
• infrared waves- grills, toasters, heaters, remote controls, night vision
• visible light- vision, photography
• ultraviolet waves- fluoresent lamp and security coding, sunbed
• x-rays- shadow pictures of bones and metals
• gamma rays- killing cancer cells, sterilising instuments, killing bateria on food.

UVA- passes through glass, penetrates deep into skin , causing wrinkles, cancer and sunburn

UVB- mostly absorbed by th ozone layer and the atmosphere

UVC- almost all is absorbed by the ozone layer and the atmosphere- MOST DAMAGING.

The higher the frequency of the waves the more damage they will cause with excessive exposure.. Gamma have the highest frequency and radio waves have the lowest.

People have many concerns regarding the risks of mobile phones, due to the high exposure of waves.

...is produced when something vibrates backwards and forwards. The sound waves are longitudinal, travel at the speed of sound and cannot pass through a vacuum.

Ulatrasound waves have hight frequencies .

Analogue- signals vary continuously in amplitude and/or frequency. Your voice is an analogue signal because it is a sound wave with many different levels of loudness (amplitude) and pitch (frequency)

Digital-signals do not vary. The amplitude and measured at regular intervals.The sampled measurements are turned into a digital code called a binary

The use of optical fibres enables the transmissio of large amounts of information over greater distances at quicker speeds; the information is carried on light waves making use of total internal reflection.

The Earth's surface is split into several large tectonic plates, which are moving slowly (few cm a year). It is these movements that cause earthquakes.

A tsunami or tidal wave, is caused by an underwater disturbance, normally an earthquake or volcano.

It is very difficult to predict when volcanos will occur because the plates do not move in regular patterns.

Seismic waves-are vibrations in the Earth which can cause massie destructio.

Primary Waves (p waves)occur first and are longitudinal : the ground is made to vibrate in the same direction as the wave is travelling. They can go through all layers on the earth.

Secondary Waves (S waves) - occur every second and are slower than P waves, they are transverse waves, the ground is made to vibrate at right angles.

absorption- a  substances abilty to absorb energy

mutation-a change in the genetic material of a cell

infrared-a region of electromagetic spectrum just below the red end of the visible spectrum

reflection-the deflection of a ray of light when it hits the boundary between two different surfaces, eg air and glass as in a mirror.