transverse and longitudinal waves Flashcards
Longitudinal waves show areas of compression and rarefaction. What are these
compression are regions of high pressure due to particles being close together
Rarefaction are regions of low pressure due to particles being spread further apart
electromagnetic waves features
Transfer energy as radiation from the source of the waves to an absorber
Can travel through a vacuum such as space
Travel at the same speed through a vacuum or the air
they move at the speed of light/ 300,000km/s
Radio waves uses
communication such as television and radio
What properties do radio waves have that make them ideal for human communication
are easily transmitted through air. They do not cause damage if absorbed by the human body, and they can be reflected to change their direction these properties make them ideal for communications
Radio waves features
Can be produced by oscillations in electrical circuits. When radio waves are absorbed by a conductor, they create an alternating current. This electrical current has the same frequency as the radio waves. Information is coded into the wave before transmission which can then be decoded when the wave is received. Television and radio systems use this principle to broad cast information
Microwaves uses
cooking food and for satellite communications
Microwaves features
high frequency microwaves have frequencies which are easily absorbed by molecules in food. The internal energy of the molecules increases when they absorb microwaves, which causes heating. Microwaves pass easily through the atmosphere, so they can pass between stations on earth and satellites in orbit
Infrared uses
Infrared light is used by electrical heaters, cookers for cooking food, and by infrared cameras which detect people in the dark.
Infrared features
Infrared light has frequencies which are absorbed by some chemical bonds. The internal energy of the bonds increases when they absorb infrared light, which causes heating. This makes infrared light useful for electrical heaters and for cooking food. All objects emit infrared light. The human eye cannot see this light but infrared cameras can detect it. This ‘thermal imaging’ is useful for detecting people in the dark.
visible light uses
Visible light is the light we can see. It is used in fibre optic communications, where coded pulses of light travel through glass fibres from a source to a receiver.
UV features
We cannot see ultraviolet light but it can have hazardous effects on the human body. Ultraviolet light in sunlight can cause the skin to tan or burn.
UV uses
Fluorescent substances are used in energy-efficient lamps - they absorb ultraviolet light produced inside the lamp, and re-emit the energy as visible light.
EM in medicine
Changes in atoms and their nuclei can cause electromagnetic waves to be generated or absorbed. Gamma rays are produced by changes in the nucleus of an atom. They are a form of nuclear radiation. 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.
Ultraviolet waves, X-rays and gamma rays are types of ionising radiation. They can add or remove electrons from molecules, producing electrically charged ions. Ionisation can have hazardous effects on the body:
What are these hazardous effects
ultraviolet waves can cause skin to age prematurely and increase the risk of skin cancer
x-rays and gamma rays can cause the mutation of genes, which can lead to cancer
