P13(Electromagnetic Waves) Flashcards
What are electromagnetic waves
Electromagnetic waves are electric and magnetic disturbances that can be used to transfer energy from a source to an absorber
What is the electromagnetic spectrum made up of (in order of decreasing and increasing wavelength and energy)
-radio waves
-microwaves
-infrared radiation
-visible light
-ultraviolet Waves
-X-rays and gamma rays
White light contains…
All the colours of the visible spectrum
What is infrared radiation used for
-remote control handsets
-medical equipment
-night vision
What are microwaves used for
-communications
-microwave ovens
What are radio waves used for
-communications
-to connect to wireless devices
The shorter the wavelength of radio and microwaves …
-the more information they can carry
-the shorter their range
-the less they spread out
What are carrier waves
-Waves that are used to carry information
-they do this by varying their amplitude
How are signals transmitted and detected
-An oscillator supplies carrier waves to the transmitter in the form of an alternating current
-The audio signal is supplied to the transmitter where it’s used to modulate the carrier waves
-the modulated carrier waves from the transmitter are supplied to the transmitter aerial
-the varying alternating current supplied to the aerial causes it to emit radio waves that carry the audio signal
-the radio waves are absorbed by a receiver aerial
-the receiver circuit separates the audio signal from the carrier waves
What are optical fibres
Thin transparent fibres that are used to transmit communications signals by light and infrared radiation
What are ultraviolet waves used for
Tanning beds
What are the dangers of ultraviolet waves
-cause blindness
-harm the skin
How are X rays produced
When electrons or other particles moving at high speeds are stopped
How are gamma rays produced
Produced by Radioactive substances when unstable nuclei release energy
What are X rays used for
Used in hospitals to make x ray images
