More uses of EM waves

Question 1

What are optical fibres ?

Answer 1

thin glass or plastic fibres that can carry data over long distances as pulses of visible light

They work because of reflection, light rays are bounced back and forth until they reach the end of the fibre

Visible light is used in optical fibres because it is easy to refract light enough so that it remains in a narrow fibre

Light is also not easily absorbed or scattered as it travels along a fibre

Question 2

What is florescence ?

Answer 2

property of certain chemical where UV is absorbed and then visible light is emitted. That’s why fluorescence colours look so bright = emit light

Question 3

What does fluorescent light generate ?

Answer 3

UV radiation where its absorbed and re emitted as visible light by a layer of phosphor

Question 4

Why are fluorescent lights good ?

Answer 4

energy efficient for places which require light for long periods

Question 5

function of security pen

Answer 5

• mark property with your name, under UV light ink will glow but otherwise invisible = help police identity property

Question 6

How is UV radiation produced ?

Answer 6

by the sun and exposure to it can give people suntans

Question 7

is overexposure to UV radiation dangerous ?

Answer 7

people may go to tanning salons when its not sunny to get artificial suntans = overexposure = dangerous

Question 8

X rays - where it used ?
How does it work ?

Answer 8

radiographers in hospitals take X ray photographs to check for broken bones

X rays pass easily through flesh and no easily through denser materials like bones and metal. Amount of radiation that’s absorbed can give you x ray images.

Radiographers will use x rays and gamma rays to treat people with cancer. High doses of these rays kill living cells so they’re carefully directed to cancer cells to avoid killing normal healthy cells.

Question 9

Gamma rays - radiation where it used ?
How does it work ?
Why is it good ?

Answer 9

used as medical tracer - gamma emitting source injected into patient and progress is followed around the body

good as it passes out through body to be detected

Question 10

X rays and Gamma rays can both be ————–

Answer 10

harmful
radiographers wear lead aprons and stands being lead screen or leave the room