P12 Flashcards
Shortest wavelength in the EM spectrum
Gamma rays
Longest wavelength in the EM spectrum
Radio waves
Use of radio waves
Connect TV, radios and phone signals
Uses of microwaves
Used for communication, carry mobile phone signals and can heat food quicker
How do microwaves heat food
Penetrate into food and are absorbed by the water molecules in the food and then they heat the food
Use of infared radiation
Remote control handset for the tv and video equipment
Use of infared radiation in medicine
Infared scanners used in medicine to detect infared radation emmited from hot spots on the body surface. These hot areas can mean the tissue underneath is unhealthy
Uses of light
Film camera (light is focused by the camera lens on to a light sensitive film)
Digital camera or a mobile phone camera, the light is focused by the lens on to a sensor
What are carrier waves
Waves used to carry any type of signal
What are optical fibres
Very thin transparent fibres that are used to transmit communication signals by light and infared radiation
How are ultraviolet waves harmful to us
Harmful to human eyes as can cause blindness and also harmful to your skin as can cause burn
Where do ultraviolet waves lie on the EM spectrum
Between violet light and x rays
Properties of x rays and gamma rays
Short wavelength
Carry much more energy per second than longer wavelentghs
How are x rays and gamma rays different
- x rays produced when electrons or other particles moving at high speeds are stopped
- gamma rays are produced by radioactive substance
- gamma rays have shorter wavelength that x rays so they can penetrate substances more than x rays
2 key uses of high energy gamma rays
Killing harmful bacteria and killing cancer cells
Microwave ovens:
Energy is transferred from a microwave source to the food in the oven, heating it
Radiant heaters:
Infrared radiation transfer energy from the heater to heat the surroundings
How do carrier waves carry information:
They vary their amplitude
How are X-rays used in hospitals?
-to make images of your internal body parts
-to destroy tumours at or near the body surface
Problems with x-rays:
Ionising radiation so can damage living tissues when passing through
How are x-rays absorbed?
By bones and teeth
Visible light:
-Wavelength ranges from 400nm-700nm
-human eye can detect visible light
White light
Light from ordinary lamps and from the sun
Radiowave range
300000Hz to 3000 million Hz
The shorter the wavelength of the waves:
-the more info they carry
-the shorter their range
-the less soread out
What happens when you speak?
You produce sound waves of different frequencies
How is signal in a microphone transmitted and detected?
1) an oscillator supplies carrier waves to the transmitter in the form of an altering current
2) audio signal is supplied to transmitter and modulates the carrier waves
3) these waves are supplied to the transmitter aerial, causing it to emit radio waves
4) they induce alternating current which causes oscillations
5) the reciever curcuit seperates the audio signal from the carrier waves, supplied to a loud speaker which then sends sound waves that are recieved by the microwave
