P1.5 Waves

Transverse Waves

All waves transfer energy from one place to another.

They are often used to communication, mobile phones, radios, TV(television). There are 2 types of waves:

1. Transverse

The vibrations that make the wave are at 90°/perpendicular to the direction the wave is travelling

Example
All waves in the electromagnetic spectrum. Transverse waves can travel through a vacuum.

Longitudinal Waves

The vibrations are in the same direction/parallel to the direction the wave is travelling.

Example

Sound waves and spectrum waves, seismic waves.

Longitudinal waves cannot travel through a vacuum.

Electromagnetic Spectrum

Electromagnetic waves are electro and magnetic disturbances which transfer energy from 1 place to another.

(longest wavelength, least energy) Radiowaves, Microwaves, Infrared, Visible-Light, UV, X-Ray, Gamma (shortest wavelength, most energy)

Properties of all electromagnetic waves

1.They all transfer energy from one place to another
2.They are all transverse waves
3.They can all be reflected, refracted and diffracted
4.They can all travel through a vacuum(space)
5.They all travel at 300,000,000 m/s in a vacuum
6.Wave Speed = frequency x wavelength
7.The shorter the wave length (the higher the frequency), the more dangerous they are.

c = f x λ
c = 300,000,000 m/s                (3 x 10^8 m/s)

Gamma Rays
Typical wavelength: 10^-12m (a million-millionth of a meter)
Sources: Radioactive substances like uranium, very dangerous
Detector: Geiger-Muller Tube

X-Rays
Typical Wavelength: 10^-10m (a ten thousand-millionth of a meter)
Sources: X-Ray tubes, very dangerous
Detector: photographic film

U-V
Typical Wavelength: 10^-8m (a hundered-millionth of a meter)
Sources: Very hot objects, sun, sparks, mercury lamps, dangerous
Detector: photographic film, causes sun tan, make fluoresent substances glow

Visible Light
Typical Wavelength: 5 x 10^-7m (a two-millionth of a meter)
Sources: Hot objects, sun, fluoresent substances, laser, LEDS
Dectector: Eyes, Photographic film, an LDR

Infrared
Typical Wavelength: 10^-5m (a hundered-thousandth of a meter)
Sources: Irons, fire, grills, toasters, warmth of hot objects
Detectors: Skin, a blackened thermometer, a thermistor

Microwaves
Typical Wavelength: 10^-3m to 10^-2m
Sources: Microwave ovens, satellites and mobile phones
Detectors: a mobile phone

Radiowaves
Typical Wavelength: 10^-1m to 10^3m
Sources: Radio transmitter, Radars, TV transmitters, bluetooth, WiFi
Detectors: Aerial with a TV set or a radio set

Electromagnetic Radiation

Radiowaves
Uses: Sending messages by radio, bluetooth, radar, communication, broadcasting
Dangers: No danger
How to reduce the danger: No need to reduce

Microwaves
Uses: To heat up objects e.g. food, detecting echoes from objects, satellites communication
Dangers: Heating water in tissue can cause 'burning' (can be absorbed by the water in the cells)
How to reduce the danger: Close door to microwave, don't let microwaves come into contact with skin. Use hands free phone, earpiece

Infrared
Uses: Firefighters use infrared viewer to look for unconscious people in smokey buildings, look for survivors from earthquake
Dangers: Causes burning of tissue (absorbed by skin, cause burn)
How to reduce the danger: Reflexs stop burns

Visible Light
Uses: To see things, light reflects into your eyes so you see colour, optical fibres
Dangers: Very bright, sensitive, light can damage eyes activites sensitive cells in retina
How…