❌ P13: Electromagnetic Waves (Y11 - Spring 1)

Question 1

What are the scientific units for standard form numbers ranging from (x^-12 to x^12)

Answer 1

terra (T) x 10^12
giga (G) x 10^9
mega (M) x 10^6
kilo (k) x 10 ^3

milli (m) x 10^-3
micro (µ) x 10^-6
nano (n) x 10^-9
pico (p) x 10^-12

Question 2

❌ What are Electromagnetic Waves (EM Waves)

Answer 2

Electromagnetic waves are transverse waves that transfer energy. The electric and magnetic waves that make up an EM wave oscillate at 90° to the direction in which the wave is travelling.

Electromagnetic waves are electric and magnetic disturbances that transfer energy from one place to another (from source to receiver)

The electromagnetic waves vary in wavelengths and frequency

Question 3

❌ Properties of all Electronagnetic Waves (What Properties Do They Share?)

Answer 3

All electromagnetic waves:

• Are transverse waves
• Transfer energy from one place to another
• Electromagnetic waves with high frequency have high energy, while low frequency waves have low energy
• They travel at a speed of 3x10^8 m/s in a vacuum.
• Electromagnetic waves can travel through a vacuum

Question 4

❌ What is the order of the electromagnetic specturm in increasing frequency order?

Answer 4

• Radiowaves
• Microwaves
• Infrared
• Visible Light
• Ultraviolet Radiation
• X ray and gamma ray radiation

Question 5

❌ Equation for the Speed of Electromagnetic Waves and the ways they can be rearrange (so the Wavelength and the Frequency are the subject)

Answer 5

Wave Speed Equation:

Wave Speed, v (m/s) = Wavelength, λ (m) x Frequency, f (Hz)

Wavelength Equation:

Wavelength, λ (m) = Wave Speed, v (m/s)/Frequency, f (Hz)

Frequency Equation:
Frequency, f (Hz) = Wave Speed, v (m/s) / Wavelength λ (m)

Question 6

❌ Calculate the wavelength of radio waves of frequency 600 million Hz. (The speed of electromagnetic waves in air = 300 million m/s.)

Answer 6

Wave Speed, v (m/s) = Wavelength, λ (m) x Frequency, f (Hz)

Wavelength, λ (m) = Wave Speed, v (m/s)/Frequency, f (Hz)

300,000,000 m/s / 600,000,000 Hz = 0.5 m

Question 7

❌ Radio waves, ultra-violet, visible light and X-rays are all types of electromagnetic radiation

Choose wavelengths from the list below to complete the table:

• 3x10^–8 m
• 1x10^–11 m
• 5x10^–7 m
• 1500 m

Answer 7

Radio Waves - 1500m

Ultra-violet Waves - 3x10^-8

Visible Light - 5x10^-7

X-Rays - 1x10^-11

Question 8

❌ Calculate the wavelength of radiation emitted from radioactive cobalt with a frequency of 2.8x10^20 Hz

+ What region would this wave lie in on the electromagnetic spectrum?

Answer 8

Part 1:

λ = v/f

3x10^8 / 2.8x10^20 = 1.07x10^-12

Part 2:

Gamma Rays

Question 9

❌ The wavelength of an argon laser output is 480 nm. Calculate the frequency of the electromagnetic wave emitted

Answer 9

f = v/λ

3x19^8 / 480x10^-9 = 0.625x10^15

0.625x10^15 = 6.25x10^14

Question 10

❌ Electromagnetic waves travel through space at a speed of 3.0x10^8 m/s.

The radio waves emitted from a distant galaxy have a wavelength of 25 metres. Calculate the frequency of the radio waves emitted from the galaxy and give the unit.

Answer 10

λ = v/f

3x10^8 / 25 = 12,000,000

Question 11

❌ How does Energy relate to Frequency with Electromagnetic Waves

Answer 11

The wave sleed equation shows you that since electromagnetuc waves all have a speed of 300 million m/s, the shorter the wavelength of the waves, the higher their frequency.

The energy of the waves increases as the frequency increases. So as the wavelengths decreases along the electromagnetic spectrum from radio waves to gamma rays, the energy and frequency of the waves increase.

Question 12

❌ Examples of Sources of Radiowaves and the Effects on the Body

Answer 12

Sources:
- Moblie phones, radio stations, and TVs all use radio waves as carrier waves. They are created when an alternating current in an electrical circuit creates an electromagnetic wave

Effects on the Body:
- They pass through the body without being absorbed

Question 13

❌ Main Use of Radiowaves and Why This Type of Radiation is suited to it’s use

Answer 13

Main Use and How it Works:
- One main use is transmitting TV signals and information. This happens as a radio wave is then sent from a transmitter to a receiver. The wave induces an AC signal in the receiver (e.g. the aerial) and the information is available to use (on your TV)

Why is this type of Wave Suited to it’s job:
- Longer wavelengths of radio waves are used because longer wavelength radio waves travel much further than short wavelength radio waves and can be used to send signals around the world.

Question 14

❌ Examples of Sources of Microwaves and the Effects on the Body

Answer 14

Sources:
- They are used for satellite communication for TVs or satellites and phone.

They are also used in microwaves.

Effects on the Body:
- Some wavelengths of microwaves can be absorbed, causing heating of cells, which may be dangerous.

Question 15

❌ Main Use of Microwaves and Why This Type of Radiation is suited to it’s use

Answer 15

Main Use and How it Works:
- An example of use is microwaves. The microwaves are able to penetrate a few centimetres into the food before being absorbed by water molecules in the food. They then transfer their energy to the water molecules causing them to heat up and cooking the food.

Why is this type of Wave Suited to it’s job:
- It’s suited to it’s use as it’s able to penetrate a few cm into food to heat it up, while it’s short wavelengths can allow it to be transmitted through the atmosphere.

Question 16

❌ Examples of Sources of Infrared Radiation and the Effects on the Body

Answer 16

Sources:
- It’s given off by all objects.

The hotter the object, the more infrared radiation is given off.

Effects on the Body:
- Infrared radiation is mostly reflected or absorbed by the skin, causing some heating too. It can cause burns if the skin gets too hot.

Question 17

❌ Main Use of Infrared Radiation and Why This Type of Radiation is suited to it’s use

Answer 17

Main Use and How it Works:
- Infra-red cameras can be used to detect the IR radiation given off by objects and monitor their temperature. They turn the infra-red wave into an electrical signal , which is then turned into an electrical signal and displayed on a screen.

Why is this type of Wave Suited to it’s job:
- This type of wave is suitable for this, as it allows hotter objects in appear brighter in images, due to the levels of radiation given off

Question 18

❌ Examples of Sources of Visible Light and the Effects on the Body

Answer 18

Sources:
- Visible light’s main use is for looking at things, and also for communication.

Effects on the Body:
- Visible light is mostly absorbed or reflected by the skin but can cause some heating effects.

Question 19

❌ Main Use of Visible Light and Why This Type of Radiation is suited to it’s use

Answer 19

Main Use and How it Works:
- Optical fibres are used for telephone and internet connections. They also have applications in medicine, by having a camera on one end of a fibre optic cable they can be used to inside the body while only requiring a small cut ot allow the optic fibre to enter the body.

Why is this type of Wave Suited to it’s job:
- Optical fibres work by bouncing light off the sides of a very narrow core. The pulse of light enters the core at a certain angle at one end and is reflected from the sides repeatedly until it emerges at the other end.

Question 20

❌ Examples of Sources of Ultraviolet Radiation and the Effects on the Body

Answer 20

Sources:
- UV radiation is produced by the Sun and UV lamps.

Effects on the Body:
- The waves have a high enough frequency, so transfer more energy, causing more damage. When it enters a living cell it collides with atoms which may knock off electrons and cause ionisation.

Question 21

❌ Main Use of Ultraviolet Radiation and Why This Type of Radiation is suited to it’s use

Answer 21

Main Use and How it Works:
- Ultraviolet radiation is also used in fluorescent lamps and other fluorescent materials. Also, security pens can be used ot mark property and when UV light is shone onto the ink it will glow, allowing stolen property to be identified.

Why is this type of Wave Suited to it’s job:
- Fluorescence is a property of certain chemicals, where UV radiation is absorbed and visible light is emitted, making it effective for making fluorscent materials.

Question 22

❌ Examples of Sources of X-Rays and the Effects on the Body

Answer 22

Sources:
- X-rays are produced when electrons or other particles travelling at high speed are stopped. X-ray tubes are used to produce X-rays.

Effects on the Body:
- Exposure to X-rays can cause cell damage, similar to UV radiation

Question 23

❌ Main Use of X-Rays and Why This Type of Radiation is suited to it’s use

Answer 23

Main Use and How it Works:
- X-rays can be used to view the internal structure of objects and materials, such as broken bones or cracks in metal objects.

Why is this type of Wave Suited to it’s job:
- The X-rays will be absorbed by dense materials, such as bone or metal, but will pass through less dense materials, such as muscle or skin, to produce an image on the detector screen.

Question 24

❌ Examples of Sources of Gamma Rays and the Effects on the Body

Answer 24

Sources:
- Gamma rays are produced by radioactive substances when unstable nuclei release energy.

Effects on the Body:
- Gamma rays are slightly ionising and therefore can caause cancer.

Question 25

❌ Main Use of Gamma Rays and Why This Type of Radiation is suited to it’s use

Answer 25

Main Use and How it Works:
- Gamma rays can be used to sterilise medical instruments or food by killing the microbes on these objects.

Why is this type of Wave Suited to it’s job:
- Gamma rays have short wavelengths and so can carry much more energy per second then longer wavelength electromagnetic waves.

Question 26

❌ What happens with the shorter the wavelength of a wave (information, range, spread out)

Answer 26

1. The more information carried
2. The shorter the range (greater absorption by the atmosphere)
3. The less they spread out

Question 27

❌ Advantages of Optical Fibres compared with Radio Waves and Microwaves

Answer 27

• Optical fibres carry much more information as light hs a much shorter wavelength than radio waves, and so can carry more pulses of waves
• Optical fibres are more secure because the signals stay in the fibre.

Question 28

❌ What is a Carrier Wave

Answer 28

A carrier wave is the continuous electromagnetic radiation, of constant amplitude and frequency, that is given out by a transmitter. The carrier wave is modulated in direct proportion to the signal, such as the voice or music, that is to be transmitted

Question 29

❌ What are Optical Fibres?

Answer 29

Optical fibres are very thin glass fibres. They are used to transmir signals carried by light or infrared radiation. The light rays can’t escape from the fibre. When they reach the surface of the fibre, they are reflected back into the fibre.

Question 30

❌ What are Carrier Waves

Answer 30

Carrier Waves are the waves used to carry any type of signal. They could be radio waves, microwaves, infrared radiation, or visible light. The type of waves used to carry a signal depends on how much information is in the signal and the distance the signal has to travel. For example, microwaves are used to carry signals via satellites to didtant countries.

Question 31

❌ Why is the radio and microwave specrum divided into bands of different wavelength ranges.

Answer 31

This is because the shorter the wavelength of the waves:

• the more information they carry
• the shorter their range (due to increasing absorption by the atmosphere)
• the less they spread out

Question 32

❌ What are examples of how microwaves and radio waves of different wavlengths are used for different communication purposes (Microwaves, 1m radio waves, 1-100m radio waves, and 100m+ radio waves)

Answer 32

• Microwaves are used for satellite phone and TV links, and satellite TV broadcasting. This is because microwaves can travel between satellites in space and the ground. Also, they spread out less than radio waves do, so the signal doesn’t weaken much
• Radio waves of wavelengths less than about 1 meter are used for TV broadcasting for TV masts becayse they can carry more information than longer radio waves
• Radio waves of wavelengths from about 1 meter up to about 100m are ysed by local radio stations (and for the emergency services) because their range is limited to the area round the transmitter.
• Radio waves of wavelengths greater than 100m are used by national and international radio stations because they have a much longer range than short-wavelength radio waves

Question 33

❌ Why does more research need to be conducted into how electromagnetic radioation may affect people’s brains

Answer 33

A mobile phone send out a radio signal when you use it. If the phone is very close to your brain, some scientists think the radiation might affect the brain. Because children have thinner skulls than adults, their brains might be more affected by mobile phone radiation. A UK government report published in May 2000 recommmended that the use of mobile phones by children should be limited. More research needs to be conducted to find out if mobile phone users are affected.

Question 34

❌ How are the sound waves you produce in a radio station microphone sent to the loudspeaker of your radio at home?

Answer 34

In the radio station, the microphone produces an altrbating current called an audio signal when sound waves reach it.

• An oscillator supplies carrier waves to the transmitter in the form of an alternating current (a current that repeatedly reverse its direction)
• The auido signal is supplied to the transmitter where it’s used to modulate the carrier waves.
• The modulated carrier waves from the transmitter are supplied to the transmitter aerial. The varying alternating current supplied to the aerial causes it to emit radio waves that carry the audio signal.
• When the radio waves are absorbed by a reciever aerial, they inducd an alternating current in the reciever aerial, which causes oscillations in the reciever. The frequency of the oscillations is the same as the frequency of the radio waves
• The reciever circuit separates the audio signal from the carrier waves. The audio signal is then supplied to a loudspeaker, which sends out sound waves similar to the sound waves recieved by the microphone in the radio station

Question 35

❌ Where do Ultraviolet Waves lie on the EM Spectrum

Answer 35

UV waves lie between violet light and X-rays in the electromagnetic spectrum. Some chemicals emit light as a result of absorbing ultraviolet waves. Posters and ink that glow in ultraviolet light contain these chemicals. Security marker pens containing this kind of ink are used to mark valuable objects. The chemicals absorb ultraviolet waves and then amit visible light

Question 36

❌ How Can Ultraviolet Waves be harmful

Answer 36

Ultraviolet waves can cause blindness. UV wavelengths are smallee than visible light wavelengths. UV waves carry more energy than visible light waves.

Ultraviolet waves are harmful to your skin. For example, too much UV directly from the Sun or from a sunbed can cause sunburn and skin cancer. It can also age the skin prematurely.

Question 37

❌ How to Prevent Being Harmed by UV Waves

Answer 37

• If you stay outside in summer, use skin creams to block UV waves and prevent them from reaching your skin
• If you use a sunbed to suntan, don’t go over the recommended time. You should also wear special goggles to protect your eyes.

Question 38

❌ How Do X-Rays and Gamma Rays have similar Properties and Why

Answer 38

X-rays and gamma rays both travel straight into substances and can pass through them if the substances are not too dense and not too thick
A thick plate of pead will stop them.

They have similar properties because they both:

• are at the short-wavelength end of the electromagnetic spectrum
• carry much more energy per second than longer-wavelength electromagnetic waves.

Question 39

❌ How Do X-Rays and Gamma Rays have differing Properties

Answer 39

They differ from each other because:

• X-rays are produced when electrons or other particles moving at hogh speeds are stopped - X-ray tubes ate used to produce X-rays
• Gamma rays are produced by radioactive substances when unstabke nuclei release energy
• Gamma rays have shorter wavelengths than X-rays, so they can penetrate substances more than X-rays can.

Question 40

❌ What are X-Rays used for

Answer 40

X-rays are often used to detect internal cracks in metal objects. These kinds of application are usually possible because the more dense a substance is, the more X-rays it absorbs from an X-ray beam passing through it. X-rays are also used un medicine to create images of broken limbs.

Question 41

❌ What 2 things are Gamma Rays used for

Answer 41

High-energy gamma rays have several important uses including:

• Killing harmful bacteria
• Killing cancer cells

Question 42

❌ How are Gamma Rays used for Killing Harmful Bacteria

Answer 42

• Bacteria waste products cause food poisoning. Exposing food to ga,,a rays kills 99% of disease-carrying organisms, including Salmonella.
• Exposing surgical instruments in sealed plastic wrappers to gamma raus kills any bacteria on the instruments. This helps stop infection spreading in hospitals.

Question 43

❌ How are Gamma Rays used for Killing Cancer Cells

Answer 43

Doctors and medical physicists use gamma-ray therapy to destroy cancerous tumours. A narrow beam of gamma rays from a radioactive source (cobalt-60) is directed at the tumour. The beam is aimed at it from different directions to kill the tumour but not the surrounding tissue.

Question 44

❌ How Are X-Rays and Gamma Rays Dangerous

Answer 44

X-rays and gamma rays passing through substances can knock electrons out of atoms in the susbstance. The talms become charged because they lose electrons. This process is called ionisation, and so X-rays and gamma rays are examples of ionising raditaion.

If ionisation happens to a living cell, it can damage or kill the cell. For this reason, exposure to too many X-rays or gamma rays is dangerous and can cause cancer. High doses kill living cells, and low doses cause gene mutation amd cancerous growth.

People who use equipment or substances that produce any form of ionising radiation (e.g, X-rays or gamma rays) must wear a film badge. If the badge shows that it is over-exposed to ionising radiation, its wearer is not allowed to continue working with the equipment for a period of time.

Question 45

❌ How do X-Rays work

Answer 45

X-rays are electromagentic waves at the short-wavelength end of the electromagentic spectrum. They are produced in an X-ray tube when fast-moving ekectrons hit a target. Their wavelengths are about the eame as the diameter of an atom.

Question 46

❌ How is a radiograph made

Answer 46

To make a radiograph or an X-ray protograph, X-rays from an X-ray tube are directed at a patient. A light-proof cassette containing a photographic film or plat-panel detector is placed on the ofher side of the patient.

Question 47

❌ Give 2 advantages of using X-rays

Answer 47

• Can easily diagnose conditions - such as tumours - with out surgery
• X-rays can kill cancer cells. Directing an X-ray beam onto skin cancer cells, or cancer cells inside the body, can help to cure cancer

Question 48

❌ Give 2 disadvantages of using X-rays

Answer 48

• Danger of radiation - mutates cells - causing ionisation - leading to cancer Bones absorb the radiation
• Not the best image created

Question 49

❌ What is the Radiation Dose and what 3 things does it depend on

Answer 49

All different types of ionising radiation are dangerous. The radiation dose received by a person is a measure of the damage done to their body by ionising radiation.
It depends on:

● the type of radiation used
● how long the body is exposed to it
● the energy absorbed per second by the body

Question 50

❌ State one advantage and one disadvantage of a CT scanner in comparison with an ordinary X-ray machine

Answer 50

Advantage:
A CT scan distinguishes between different types of soft tissue; and ordinary X-ray machine does not. (A CT scanner can give a three-dimensional image whereas an ordinary X-ray image is two-dimensional)

Disadvantage:
The radiation dose from a CT scan is much greater than from an ordinary X-ray imaging machine (CT Scanners are much more expenive to buy and operate than ordinary X-ray machines)

Question 51

❌ What are Ultrasound waves used for in Medicine

Answer 51

Ultrasound scanning and the destruction of kidney stones

Question 52

❌ What precautions are used when taking X-rays

Answer 52

• Patients are limited to the number of X-rays they are allowed to have
• Shielded walls containing lead are built into all X-ray rooms to protect people outside the room.
• Only trained specialist staff - called radiographers - are allowed to use X-ray machines

Question 53

❌ What might low doses of x-rays cause?

Answer 53

Low does of X-rays may cause cancer

Question 54

❌ What are Ultrasound waves used for prenatal scanning

Answer 54

Ultrasound waves are not ionising, and so they are safe to use when performing a natal scan.

Question 55

❌ Why are ultrasound waves partly reflected by body organs

Answer 55

The organs have a different density to the surrounding tissue. So ultrasound is reflected at the tissue/organ boundaries.

Question 56

❌ Why is an Uktrasound scannee bettee for than an X-ray scanner for scanning a body organ

Answer 56

X-rays cannot dofferntiate different tissues easily and ultrasound does not cause damaging ionisation.