P13 Electromagnetic Waves Flashcards
What order does the electromagnetic spectrum go in
In order of decreasing wave length and increasing frequency and energy
What is the electromagnetic spectrum made up of
Radio waves Microwaves Infrared radiation Visible light (red to violet) Ultraviolet X-rays and Gamma rays
What wavelength can the human eye detect?
Visible light (ranges from 400nm to above 700nm)
How do electromagnetic waves transfer energy
From a source to an absorber
Wave speed equation:
V= frequency x wavelength
What colours does whit light contain
All the colours on the visible light spectrum
Infrared radiation uses?
Carrying signals from remote control handsets and inside optical fibres
Microwaves uses?
Carry statelite TV programmes and mobile phone calls.
Heating food
Radio waves uses?
Radio and TV broadcasting, radio communications and mobile phone calls
What is mobile phone radiation
Microwave radiation, and is also radio waves at near micorwave frequencies
Why are radio waves of different frequencies used?
They have different purposes, because the wavelength (and so the frequency) of waves affects: how far they travel, how much they speard out, and how much information they carry.
How are microwaves used for communication?
Used for satellite TV signals
Are mobile phones safe to use?
Further research is required to evaluate wether or not they are safe, however micro and radio waves can heat the internal parts of people’s bodies and infared radiation can cause skin burns.
What are Carrier waves?
Waves that are used to carry information. They do this be varying their amplitude
Optical fibres?
Very thin transparent fibres that are used to transmit communication signals by light and infrared radiation. Light rays cant escape when they reach the surface of the fobre they just reflect back into the fibre.
How does optical fibres compare to radio waves and microwaves?
Optical fibres carry much more information as light has a much shorter wavelength, than radio waves, and so can carry more pulses of waves.
They are more secure because the signals stay in the fibre
What effect does ultraviolet rays have?
They have shorter wavelengths than visible light and so carry more energy, can harm the skin and eyes. Causes blindness and to much UV from the sun or a sunbed can cause sunburn and skin cancer, and can also age your skin prematurely.
How do you control Ultraviolet radaition (prevent harm to your skin and eyes)?
If stay outdoors in summer, use skin creams block UV wavesand prevent them reaching your skin.
If you use sunbed to get a suntan, don’t go over the recommended time. You should also wear special googles.
Why do x-rays and gamma rays have similar proporties?
Are at the short-wavelength end of the spectrum
Carry much more energy per second than other longer waves
How does x-rays and gamma rays differ from each other?
X-rays are produced when electrons or other particles moving at high speeds are stop- X-ray tubes are used to create x-rays
Gamma rays produce by radioactive substances when unstable nuclei releases energy. Gamma rays have a shorter wavelength than x-rays, so they can penetrate substances more than x-rays can.
What are gamma rays used for?
To kill harmful bacteria in food, to sterilise surgical equipment, and to kill cancer cells.
Ionisation
X-rays and gamma rays passing through substances can knock electrons out of atoms in the substance. The atom then becomes charged because they lose electrons. X-rays and gamma rays are examples of ionising radiation
How does ionising radiation effect living things?
It can damage or kill the cell. High doses kill living cells and low doses cause gene mutation and cancerous growth.
How do people that use equipment or substances that produce any form of ionsing radiation cope?
They must wear a film badge. If it shows it is over exposed to ionising radiation the wearer is not allowed to continue working with the equipment for a period of time
How are x-rays dangerous?
They are a form of ionising radiation amd so can damage living tissue when they pass through it
What are x-rays mostly absorbed by?
Bones and teeth rather than by soft tissue
What is radiation dose?
Is a measure of the damage done to their body by ionising radiaton.
What does radiation does depend on?
The type of radiation used
How long the body is exposed to it
The enrgy per second absorbed by the body from the radiation
What are x-rays used in hospitals for?
Make images of your internal body parts
Destroy tumours at or near the body surface
X-ray therapy
Doctors use this to destroy cancerous tumours in the body. Thick plates between the x-ray tubes and the body stop x-rays reaching healthy body tissues. A gap between the plates allow x-rays through to reach the tumour. X-rays in therapy are shorter than x-rays used for imaging.
How can you take an x-ray of an organ that consists of soft tissue?
It can be filled with a substance called a constant medium, that absorbs x-rays easily. This enables the interal surface of the organ to be seen on the radiograph. E.g for the stomach a patient is given a barium meal before x-ray machine is used (barium compound good absorber of x-rays)
What is used to stop x-rays reaching other parts of the patient’s body
Lead plates, the x-rays raeching the patient pass through the gaps between the plates (lead is a good absorber of x-rays).
Visible light uses?
Optic fibres
Astronomy
Photography
Ultra Violet used for?
Sterilisation
What are x-rays used for?
Security, Medical reasons
Gamma rays used for?
Cancer treatment
