EM spectrum

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What is the order of the EM spectrum?
Radio wave. Micro wave. Infra red. Visible light. Ultra violet. X-rays. Gamma rays
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what happens as the EM spectrum goes up?
The frequency increases and the wavelength decreases
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What happens to EM waves in a vacuum?
The all travel at the same speed
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who discovered infra red?
Herschel in 1800
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How did he discover infra red?
He wanted to know the temperature of each colour of visible light when split. Noticed they increased. Measured past red end of the spectrum. Highest temperature, infra red radiation
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Who discovered ultraviolet?
Ritter soon after 1801
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How did he discover this?
Knew that silver chloride turned from whit to black in light. Measure time in different lights. Quickest at blue end. Just past blue end turned quickest. Ultraviolet radiation
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What depends on a waves frequency?
How it is absorbed, reflected or transmitted
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What does a higher frequency mean?
More energy and so the radiation is more harmful
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How are Microwaves harmful to people?
Similar frequency to vibrations of molecules, increases vibrations resulting in heating. Can heat human body cells
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How is infra red harmful to people?
Like microwaves has a heating effect. Higher frequency - more energy. Cause skin burns
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How is ultraviolet harmful to people?
It has more energy and is ionising. knock electron off atoms. can cause skin burn, skin cancer and eye damage
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How are gamma rays harmful to people?
More energy, ionising. more damaging penetrate further into the body. Cell mutation/damage - leading to tissue damage or cancer
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What are radio waves used for?
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What do short-wave radio signals do and why?
Short-wave radio signals reflect off of the Ionosphere as they have to stay in strait lines for TV and radio transitions. Some can pass through the Ionosphere and communicate with satelliets
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What do long-wave radio signals do and why?
Long-wave radio signals diffract (bend) round the earth. they can be transmitted from London and revived half way round the world
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How to microwave transitions work?
A signal is sent to an orbiting satellite and transmits it back in a different direction so it is revived by a satellite dish on the ground
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How do microwave ovens work?
Microwaves are absorbed by water molecules so the food is able to heat up. A different wavelength is used from satellite communications. After being absorbed the heat is conducted or convected to other parts of the food
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How is infrared radiation used to monitor temperature?
Infra red is know as heat radiation. The hotter an object the more IR it gives out. This means infra red sensors can detect heat. Can also be detected by night vision equipment that turns it into electrical signals shown on a screen
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How do optical fibres work?
Waves are bounced off of the sides of the thin inner core of glass or plastic. It enters on end is reflected repeatedly and emerges the other end
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What are other uses of infra red?
Used in cooking - grills, toasters. Remote controls. Mobile phones/computers-short distances. Security systems
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How does visible light work?
when light enters the eye it is refracted by the lens and focused on the retina at the back of the eye and the brain interprets it
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What can Ultraviolet light be used to identify?
Real and fake bank notes. Real notes have a special marking. Fake notes are printed on slightly florescent paper meaning they all light up
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How do x-rays in a hospital work?
X-rays pass easily through flesh but not through denser materials such as bones. The amount absorbed/not absorbed forms an image
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What are some other uses of x-rays?
Luggage scanning and passenger scanning
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What might a radiographer do to protect themselves from x-rays?
Wear lead aprons, stand behind a lead screen or leave the room
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How can Gamma rays detect cancer?
A radioactive isotope is injected into the patient. A gamma camera is used to form an image. This shows where the cancer might be
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What are other uses of Gamma rays?
Sterilisation of food and surgical instruments
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What are the types of ionising radiation?
Alpha, Beta and Gamma
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Why is ionising radiation dangerous?
They knock electrons off of atoms. This causes ionisation which damages or destroys molecules. Can lead to cancer
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Other cards in this set

Card 2


what happens as the EM spectrum goes up?


The frequency increases and the wavelength decreases

Card 3


What happens to EM waves in a vacuum?


Preview of the front of card 3

Card 4


who discovered infra red?


Preview of the front of card 4

Card 5


How did he discover infra red?


Preview of the front of card 5
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