P13 Electromagnetic waves

Question 1

The electromagnetic frequency from lowest frequency to highest frequency:

Answer 1

radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays

Question 2

What is the human eye ranges?

Answer 2

350nm-650nm in the visible light spectrum

Question 3

What do Electromagnetic Waves do?

Answer 3

Transfer energy as radiation from a source to an absorber.

Question 4

What are radio waves used for?

Answer 4

Radio waves are used for sending radio and television signals.

Question 5

What are microwaves used for?

Answer 5

As well as heating food in microwave ovens, microwaves are used for communication. For example, mobile phones, and wireless internet (Wi-Fi) devices like laptop computers all use microwaves to communicate. Microwaves are also used for sending satellite signals, eg for
GPS
systems or satellite television.

Question 6

What is Infrared used for?

Answer 6

They are also used for communication, including remote controls for televisions and stereos, as well as sending internet and telephone signals along optical fibres. Infrared waves can also be detected by infrared cameras, so are often used by night vision cameras or thermal imaging cameras in police helicopters – which can detect the infrared waves emitted by people and animals.

Question 7

All warm object emit

Answer 7

Infrared radiation

Question 8

What is visible light used for?

Answer 8

Forming images in cameras and video cameras. Concentrated visible light emitted by
lasers. Also used in Remote controls.

Question 9

What are carrier waves?

Answer 9

Any waves that can transmit information by carrying a signal. They do this by varying their amplitude.

Question 10

The shorter the wave, the _______:

Answer 10

more information they can carry
lesser the spread
shorter the range

Question 11

What are optical fibres?

Answer 11

Optical fibres are thin transparent fibres that are used for communication and use light or IR radiation and can carry more information because they are shorter wavelengths and have bigger range than normal short wavelength radiation because the fibres extend the length and stop them being absorbed.

Question 12

Why are optical fibres more secure?

Answer 12

signals totally internally reflected so cannot escape from fibre except at
receiver end,
radio signals travel through air so detected by any radio detector in their
path

Question 13

Why do shorter wavelength/high frequency em radiation carry more information?

Answer 13

waves have a much higher frequency,
carry more pulses per second

Question 14

(UV) Ultraviolet radiation:

Answer 14

Ultraviolet (UV) waves are used in
forensic science
to help detect forged documents, like fake banknotes, passports or driving licences. Ultraviolet waves can be
absorbed
by some materials, like fluorescent inks in highlighter pens, making them glow brightly. They are also used to disinfect water, by killing bacteria.

Question 15

X-RAY radiation:

Answer 15

X-rays are commonly used to produce medical images of broken bones, because they can pass through body tissues but are absorbed by bones. They are used to sterilise medical equipment, killing any bacteria present before the instruments are used for surgery. X-rays are also used in airport security scanners and to detect structural faults and cracks.

Question 16

Gamma rays:

Answer 16

Gamma rays are also used to produce medical images and to sterilise medical instruments, in a similar way to X-rays. They are also used to sterilise food, killing bacteria in fresh fruit and vegetables to increase their shelf life. Gamma rays can also be used to detect and even to treat cancer.

Question 17

Dangers of the EM spectrum to the human body:

Answer 17

Microwaves
Because microwaves have a heating effect, some powerful microwaves can be dangerous. Your microwave oven will not switch on if the door is open, to prevent the microwaves causing damage to the cells in your body by heating them.

Infrared
The heating effect of infrared waves can cause burns to your skin.

Visible light
Concentrated visible light (eg from a laser or the Sun) can cause eye damage or even blindness.

Ultraviolet
Ultraviolet (UV) radiation can cause eye damage, which is why most sunglasses can absorb UV, preventing it from reaching the eye. The intense UV emitted by the Sun is absorbed by your skin and can cause sunburn or even damage DNA in your body cells – which could lead to skin cancer.

X-rays
X-rays can also damage DNA in body cells, which could lead to cancers developing inside the body. For low levels of exposure (eg a few medical x-rays per year) this is not a significant problem, but radiographers and other people working with X-rays must take precautions to reduce this risk.

Gamma rays
Like X-rays, gamma rays can also damage DNA in your body cells which can lead to cancers developing inside the body. People working with radioactive substances which emit gamma rays must limit the amount of gamma radiation they are exposed to, by wearing protective clothing and restricting the time they work near these materials.

Question 18

What is ionisation and how does it relate to Xrays and Gamma rays.

Answer 18

Ionisation is process of making uncharged atoms become ions which
are charged atoms
occurs when X-rays or gamma radiation pass through substances,
as X-rays and gamma radiation knock electrons out of uncharged
atoms.

Question 19

Which metal absorbs gamma and x-ray radiation

Answer 19

lead metal

Question 20

How do X ray machines work?

Answer 20

-An X-ray tube is switched on an X-ray waves pass through the body
-Bones and teeth absorb x rays and organs can be filled with a substance called a contrast medium to be able to absorb x rays.
-The film/flat panel detector detects the x rays that pass through and a charge coupled device(CCD) converts the x ray image to light. The image is a negative image where the areas the x ray is detected is dark while the organ/bone where x-rays are absorbed looks light.

Question 21

Why is radio waves of different wavelength used?

Answer 21

Used for different area sizes e.g local-metropolitan etc