# physics unit 3 waves

physics unit 3 waves

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• Created by: jesper
• Created on: 31-03-12 06:05

## There are two types of waves:

Mechanical waves (waves that need a material meduim to travel through, solid liquid or gases)
Electromagnetic or EM waves (Are waves that do not need matter like mechanical waves they travel through a vacuum)

Mechanical waves can be two types:
Transverse waves- In transverse waves the meduim moves at a right angles to the direction of the motion of the wave.

Longitudinal waves- In longitudinal waves the meduim moves in the same direction as the motion of the wave.

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## Key definitions

Wavelength= is the distance between the corresponding points in the wave – one crest to the next crest is a transverse wave

Amplitude= is the maximum displacement of a part of the medim from its rest point.

Period= is the time for one complete cycle of the wave form

Frequency= is the numver of cycles of the waveform each second

frequency= (1/period)

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## Wave equation:

Wave equation:

Wave speed= frequency * Wavelength

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## Electromatic spectrum

Electromatic spectrum
Radio waves – Microwaves – Infra-red – visible light – Ultra – violet – X-rays – Gamma rays

use: is used for communication of information.
Microwaves
use: is used for heating food and also for satellite communication and radar (used to detect aircraft and shipping)
Danger: Can directly heat internal body tissue, so serious damage can occur before pain is felt. Microwave cookers have a cut-out which turns off the microwavve radiation when the cooker door is openend.
Infrared
use: is used in heating devices and night vision cameras.
Danger: is readily absorbed by our skin and can result in burns. Therefore people finding themseves working in enviroments where exposure to these radaitaion is possible were specail suites.
Visible light
use: is used by humans to see things such as in photography and in some types of fibre optics to look inside human bodies when diagnosing and treating medical conditions.
U
ltraviolet
use: is used in fluorescent lamps, disco ‘black’ lights and sterilising water.
Dangers: is responsibl for skin cancer and damage to the eye
X rays
use: are used to examine the internal structures of the body in medical diagnosis and to investigate the crystal structure of materials in manufacturing
Dangers: can produce cell mutation and cancer.
Gamma rays
use: used to treat certain types of cancer.
Dangers: Also can cause cell mutation and cancers.

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## Analogue and Digital signals.

Analogue electrical signals: are continously variable voltages.

Digital electrical signals: can either only have two possibel values. These represent the digits 0 and 1 in the binary system.

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## Light waves

Light waves

The incident ray is the ray hiiting the mirror. The reflected ray is the one that came of the mirror.

The normal is a construced line drawn at right angles to the mirror surface where rays of light strikes it.

Angle of incidence= i
Angle of reflection= r

Law of reflection=
The angle of incidence = the angle of reflection

Refraction of light is the bending that hapepens when light travels from one material into another. Like from air into glass.

Critical angle= light arriving at a boundary between ant material, in which light travels more slowly than in air, and air at an angle greater than the crictical ange is totally internally reflected.

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## Sound waves

Sound waves

The range of frequencies that a human ear can detect is from 20hz to 20khz, these are referred to as audio frecuencies.

The louder the sound the greater the amplitude. Nthe more waves on the screen the higher the notes.

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