| Describe Longitudinal Waves (in terms of Vibration direction & Particle movement) & Examples | 1) the vibrations are parallel to the direction of wave travel (undergo compression & rarefaction):
2) Particles move backwards and forwards between compressions as the wave is transmitted through the medium
EXAMPLES:
- sound waves
- ultrasound waves
- seismic P-waves |
| Describe Transverse waves (in terms of Vibration direction & Particle movement) & Examples | 1) the vibrations are at right angles to the direction of wave travel
2) Energy is transferred from left to right. However, the particles move up and down as the wave is transmitted through the medium
- ripples on the surface of water
- vibrations in a guitar string
- a Mexican wave in a sports stadium
- electromagnetic waves - eg light waves, microwaves, radio waves
- seismic S-waves |
| 4 Properties of Electromagnetic waves | 1-Transverse, their vibrations are changes in electrical and magnetic fields at right angles to the direction of wave travel. They all:
- transfer energy as radiation from the source of the waves to an absorber
- can travel through a vacuum such as in space
- travel at the same speed through a vacuum or the air
- travel at 300 million metres per second (m/s) through a vacuum. |
| Whats the relationship between wavelength size & frequency(& energy) | - waves with a very short wavelength, high frequency and high energy
- waves with a very long wavelength, low frequency and low energy |
| 7 key features of Radio waves | 1) used for communication e.g. television and radio
2) transmitted easily through air
3) do not cause damage if absorbed by the human body
4) can be reflected to change their direction
5) can be produced by oscillations in electrical circuits
6) When radio waves are absorbed by a conductor, they create an alternating current the electrical current has the same frequency as the radio waves
7) Information is coded into the wave before transmission, which can then be decoded when the wave is received |
| 4 key features of Microwaves | 1) used for cooking food and for satellite communications
2) High frequency microwaves have frequencies which are easily absorbed by molecules in food
3) The internal energy of the molecules increases when they absorb microwaves, which causes heating
4) Microwaves pass easily through the atmosphere, so they can pass between stations on Earth and satellites in orbit |
| 5 key features of Infrared | 1) used by electrical heaters, cookers for cooking food, and by infrared cameras which detect people in the dark
2) has frequencies which are absorbed by some chemical bonds
3) The internal energy of the bonds increases when they absorb infrared light, which causes heating
4) All objects emit infrared light
5) Can be detected by infrared cameras. This 'thermal imaging' is useful for detecting people in the dark |
| Use of Visible Light | 1) used in fibre optic communications, where coded pulses of light travel through glass fibres from a source to a receiver |
| 3 key features of Ultraviolet | 1) can have hazardous effects on the human body
2) in sunlight can cause the skin to tan or burn
3) Fluorescent substances are used in energy-efficient lamps - they absorb ultraviolet light produced inside the lamp, and re-emit the energy as visible light |
| How are Electromagnetic waves Used in medicine? | 1) Changes in atoms and their nuclei can cause electromagnetic waves to be generated or absorbed
2) Gamma rays are produced by changes in the nucleus of an atom, they're a form of nuclear radiation
3) High energy waves such as X-rays and gamma rays are transmitted through body tissues with very little absorption. This makes them ideal for internal imaging. X-rays are absorbed by dense structures like bones, which is why X-ray photos are used to help identify broken bones |
| 5 key features of Ionising radiation | 1) Ultraviolet waves, X-rays and gamma rays are types of ionising radiation
2) They can add or remove electrons from molecules, producing electrically charged ions
3) Hazardous effects of Ionisation on the body:
- UV waves can cause the skin to age prematurely and increase risk of cancer
- x-rays and gamma rays can cause gene mutation, which can lead to cancer
4) radiation dose - a measure of the risk of harm caused by exposing the body to ionising radiation (Sv). As radiation dose figures are generally small, they are usually given in millisieverts (mSv)
5) background radiation - around us all the time:
- radioactive rocks in the Earth's crust
- cosmic rays from space
- man-made sources such as nuclear weapons fallout and nuclear accidents
Affected by: jobs, where people live |
