P13-Electromagnetic waves Flashcards
What is the order of the electromagnetic spectrum?
Radio waves, microwaves, infrared, visible light, ultraviolet radiation and x rays and gamma radiation.
What wavelength can the human eye detect?
Only visible light at a wavelength of 400 to 700.
What is the wave speed equation?
Wave speed(m/s) = Frequency(Hz) x wavelength(m)
What is white light?
It is light from ordinary lamps and from the sun, it has all the colours of the visible spectrum in it.
What is infrared radiation?
All objects emit it and the hotter an object is, the more infrared radiation it emits. It is absorbed by your skin and can damage, burn or kill skin cells as it heats them up.
What are 3 devices that use infrared radiation?
Optical fibres in communications, remote control handsets for TV controls and infrared scanners that are used in medicine.
What are microwaves?
It has a shorter wavelength than radio waves and people use them for communications in satellites and ovens, as they heat food faster than ordinary ovens.
What are radiowaves?
They are used to carry radio, TV and mobile phone signals.
What does the frequency of radio waves affect?
How far they can travel, how much they can spread and how much information they can carry.
How do carrier waves work?
They start with an oscillope which sends out a frequency to the transmitter, which goes to the receiver, which absorbs the energy then to the oscillope at the other end, which lets us see the frequency so can be used to transfer messages.
What is UV?
It is between violet light and X-rays in the spectrum. They are harmful to human eyes and can also be harmful to your skin.
What are X-rays and gamma rays?
They are short wavelength and carry lots of energy. However it is different to gamma rays as X-rays are produced from electrons travelling at high speeds are stopped and gamma rays are produced by radioactive substances when unstable nuclei releases energy. Gamma rays also have a shorter wavelength.
How can gamma rays be used?
By killing harmful bacteria in food or surgical instruments and killing cancer cells.
How are gamma and X-rays dangerous?
As they are ionising, knocking electrons out of atoms in the substance, giving the substance a charge. This can damage cells.
Why are X-rays used?
They are used to make images of internal body parts and to destroy tumours at or near the body surface.
How do X-rays work?
They pass through soft tissues but are absorbed by bones, teeth and metal objects. The image starts white when the radiation passes through it turns black so we can see the bones.
What does the radiation dose depend on?
The type of radiation used, how long the body is exposed to it and the energy per second absorbed by the body from the radiation.
What is X-ray therapy?
It is where doctors use it to destroy cancerous tumours in the body through the use of short wavelength X-rays. Therefore they carry more energy than imaging X-rays which do not have the energy to destroy tumours.
What are the three types of radio waves?
Long waves, short waves and very short waves.
What are UV waves used in?
They are used in lights, security and to sterilise things.
What is flourescence?
It is when UV light is absorbed and the energy is reemitted as visible light.
What is an optical fibre?
It is a thin glass or plastic tube which light is fired through, reflecting off it and going long distances. This can transmit messages. We need materials that reflect, not absorb and specular instead of diffuse reflection.
