Chapter 12 Electromagnetic Waves

Question 1

What are EM waves

Answer 1

Em waves are transverse waves that transfer energy from one place to another

Question 2

What set of properties do EM waves share

Answer 2

Travel at speed of light
Can travel through a medium
All transverse
High frequency means high energy, low frequency means low energy

Question 3

What is the electromagnetic spectrum

Answer 3

The different type of em waves and how they differ in wave length

Question 4

Em wavelengths in EM spectrum from largest wavelength to smallest
Ra…
Mi…
In…
Li…(visible)
Ul…
X-r…
Ga…

Answer 4

Radio waves
Microwaves
Infared
Visible light
Ultraviolet (uv)
X-rays
Gamma rays

Question 5

What is the range of size of EM wavelengths

Answer 5

1 kilometre to 1 picometre

Question 6

Wavespeed calculation

Answer 6

V=f x wavelength
Wavespeed(m/s) = frequency(Hz) x wavelength(m)

Question 7

Source,effect on body,one main use,how it’s suited radio waves

Answer 7

Source - alternating current in electrical circuit creating radio wave

Effect - passes through

Main use - carrys signal between phone and nearest phone mast

How it’s suited - longer wavelength so travel further than short wavelength radio waves so can send signal around the world

Question 8

Source,effect on body,one main use,how it’s suited microwaves

Answer 8

Source - mobile phones, heatinf food in microwave

Effect on body - can be absorbed heating cells may be dangerous

Main use - used for satellite communications in satellite tv or phones.signal in atmosphere transmitted due ti shirt wavelngth through atmosphere reflects from satellite sent to earth

Why it’s suited - waves penetrate food, then asborbed by water molecules so transfer energy so warms up and cooks it

Question 9

Source,effect on body,one main use,how it’s suited infared radiation

Answer 9

Source - given of by all objects the hotter the more radiation

Effect on body - reflected lr absorbed by skin causing some heating also potentially burns if skin gets to warm

One main use - can be used to cook. Temp of object increases when absorbing the infa red radiation.

Why is it suited - Ir cameras can detect Ir radiation given off by objects and monitor their temp and turn it into electrical signals to display onto screen

Question 10

Source,effect on body,one main use,how it’s suited visible light

Answer 10

Sources - main use is looking at things but for communication with signals sent along optical fibres carrying info over lomg distances as pulses of light

Effects on the body - mostly absorbed or reflected can cuase some heatinf effects

One main use and how it works - in medicine with one end of fibre optic cable a camera to see inside of the body requring a small cut

How it’s suited - Optical fibres work by bouncing light off sides of a very narrow core. The pulse of the light enters the core at a certain angle at one end and is reflected from the sides repeatdely until it emerges at the other end

Question 11

Absorbtion and emissions of ir radiation required practical method

Answer 11

1-Fill the cube with hot water

2-Then using a ruler measure a certain amount to decide how much to measure your readings from for fair and reliable results

3-Then from that certain distance using the infared thermometer measure each face’s temprature the greater the temp the greater the radiation

4-Repeat for each surface

Question 12

Absorbtion and emissions of ir radiation required practical equipment

Answer 12

Leslie box
Ruler
Infared thermometer
Boiling water to pour in from kettle
Heat proof matt

Question 13

Absorbtion and emissions of ir radiation required practical risk assessment

Answer 13

Make sure not to pour any of the boiling water over you so make sure to have it in a secure kettle/jug and pour slowly and carefully to ensure it dosen’t burn you and dosen’t get everywehere

Question 14

The shorter the wavelength of a wave means that

Answer 14

More info carried

The shorter the range(greater absorbtion by the atmosphere)

The less they spread out

Question 15

Compared with radio and microwaves optical fibres…

Answer 15

Carry much more info as light has a shorter wavelength than radio waves so carrys more pulses of waves

More secure as the signals stay in the fibre

Question 16

What’s a carrier wave

Answer 16

EM waves which is modulated to carry a signal

Question 17

Ultraviolet freuqency range,uses,dangers

Answer 17

Range - 8x10^4 x 3x10^16

Uses - sun bed/tan, fluroescent light, light bulbs

Dangers - eyes, causing blindness - can damage skin through sun burn, aging skin and skin cancer

How to protect from dangers of uv light- sun cream,sunglasses,cover skin not to too much time in sun

Question 18

Similartieis betwen x and gamma rays

Answer 18

Highest energy
Highest frequendg
Shortest wavelength

Question 19

How x rays are produced

Answer 19

When electronsare moving at a high speed they collide with a metal target producing x rays

Question 20

How are gamma rays produced

Answer 20

By radioactive substances when unstable nuclei release energy

Question 21

What are x rays used for in hospitals

Answer 21

X rays are used for x-ray therapy to destroy cancerous tumors in the body. And are also used to for x-ray photographs to see the bones in the body to see if they are broken. They can be used to see internal organs. They can do this by drinking a contrast medium for example barium what absorbs the x-rays so then you see internal organs

Question 22

Why are x rays dangerous

Answer 22

As they can cause ionisng radiation leading to cancer with high doses killing living cells while low doses can caused genetic mutation and cancerous growth

Question 23

What absorbs x rays as they pass through the human body

Answer 23

Bones,teeth,metal objects which are not to thin

Question 24

Whats a charge couples device (CCC)

Answer 24

An electronic device that creates an electronic signal from an optical image formed on the CCD’s array of pixels

Question 25

How is an x-ray image produced

Answer 25

X-rays from the tube pass through the part of the patients body under investigation. The x rays pass through soft tissue but absorbed by teeth,bones and metals in the body. The parts of the film or dectector that the x-rays reach become darker than other parts. So the bones appear lighter than the surrounding tissue, which appears dark, the radiograph shows a ‘negative image’ of the bones. Then the flat panel detector small screen that contains a CCD. The sesnors in the CCD convert x-rays to light. The light rays then create elctronic signals in the sensors that are sent to a computer, which displays a digital x ray image.