waves 2

Question 1

Radio waves

Answer 1

type of electromagnetic wave with the longest wavelength

Question 2

Wavelength of radio waves

Answer 2

greater than 30 cm

Question 3

How are radio waves produced

Answer 3

by passing an oscillating current through a long wire called the aerial

Question 4

what does the frequency of the radio wave depend on

Answer 4

same as the frequency of the oscillating current

Question 5

radio waves of different wavelengths have…

Answer 5

different properties

Question 6

are radio waves absorbed strongly by the walls

Answer 6

no so radio wave signals can be received indoors

Question 7

radio waves in transmitters

Answer 7

Sound waves are turned into oscillating crrent and then radio waves in an eariel

Question 8

radio waves receivers

Answer 8

picked up by aerails radio waves turned into oscillating current and then into sound waves

Question 9

why can some radio waves travel so far?

Answer 9

low-frequency( up to 3Mhz) radio waves can travel hundreds of miles and they travel on earth s surface. Ground waves can be used for local and national radio
Higher frequency (3-30 MHz) radio waves reflected from the ionosphere. These sky waves are used for international and amateur radio.

Question 10

Wireless network

Answer 10

Wi-fi allows us to acees the internet without any wires. It uses high frequencies that are around 2.4GHz. Wi-fi can be connected through access points and the area that they cover is the hotspot. They can be unreliable as they only cover up to 100m.

Question 11

Microwaves

Answer 11

Electromagnetic radiation and are shorter wavelength radio waves

Question 12

wavelength of microwaves

Answer 12

from 30 cm to 1mm

Question 13

How are microwaves produced

Answer 13

Long-wavelength microwaves are madde using an aerial similar to radio waves and are used fro communication
Shorter wavelength microwaves are made by a device named megnetron and are used in microwave ovens and radar equipment

Question 14

size of antennas

Answer 14

radio antennas are large because radio waves wavelength is high but a phone s antenna is small as microwaves have smaller wavelengths. For optimal efficiency, the antenna should be as large as the carrier wave’s wavelength.

Question 15

How does my mobile phone work

Answer 15

Network providers divide the area into cells and at the center of each cell is a base. Your phone sends and receives microwaves so it is a 2-way radio. These microwaves come and go at different frequencies so you can talk and hear what the other person is hearing. Once you get a weak signal from a base your phone connects to another base that gives a better signal.

Question 16

what effects my mobile phone reception

Answer 16

different factors but microwaves loose intensity as they travel so distance is also a factor. Furthermore, if there are tall buildings and create pockets without reception so low power transmitters are used to fill in the gaps.

Question 17

microwaves and staellite communication

Answer 17

they are very high-frequency (30MHz) radio waves so they are not reflected by the ionosphere but refracted thus they can be picked up by satellites and amplified and then transmitted into different countries very far away.

Question 18

ALARA priceiple preacutions

Answer 18

using a hand-free kit or shield
limit time taking on the phone
Using phone that emits less radiation
Under 16s use phones when essential

Question 19

experiment if hand free is going to make a difference

Answer 19

IV: distance from transmitter to receiver
DV: Intensity of microwaves depending on the distance
Results: as distance increases the intensity of microwaves decreases.

Question 20

how much are mobile phones mass threat to our health

Answer 20

masts are less likely to release less radiation than phones

Question 21

amplification

Answer 21

strength of a signal

Question 22

base station

Answer 22

equipment at the center of the cell that receives and transmits signals.

Question 23

visible light wavelength

Answer 23

390nm to 780nm, different wavelengths equate to different colours in the spectrum

Question 24

how is light produced

Answer 24

emitted by very hot objects, filament in a bulb is 2500 degrees celsius, in the sun nuclear fusion occurs to create light and in neon lights a current passes through gas to produce light.

Question 25

light and computers

Answer 25

computers code digital signals that can be used to send in optical fibres

Question 26

infrared waves

Answer 26

from of electromagnetic radiation that we experience everyday

Question 27

wavelength of IR

Answer 27

from 1mm to 0.0001mm

Question 28

How is IR used in remotes

Answer 28

Not all IR is thermal, short-wavelength IR are not hot and cannot be detected by the skin. Type of IR used to send signal by remotes over short distances in the air. This way IR can only go in a straight line but we can use optical fibres for IR to travel long distances and go around corners

Question 29

Digital remote control signals

Answer 29

Different signals are sent when u tap on different buttons of the remote

Question 30

total internal reflection

Answer 30

normally when a light ray hits a boundary between different density objects it refracts. This is due to the change in speed. If the angle of incidence ray is greater than a value called the critical angle then the right is reflected and it works like it is a perfect mirror. Called internal reflection.

Question 31

Why angle of incidence is important

Answer 31

When the angle of incidence is smaller than the critical angle then the light ray is refracted. If the angle of incidence is = to critical angle the light ray is refracted along the boundary. If the angle of incidence is bigger than the critical angle total internal reflection happens where light rays are reflected and it works like a mirror.

Question 32

Critical angle

Answer 32

the smallest angle of incidence at which total internal reflection occurs

Question 33

Optical fibers

Answer 33

thin strands of solid glass. Can transmit light signals at high speeds at long distances.

Question 34

Optical fibers in medicine

Answer 34

Can be used to see inside the patient without cutting them open. A device used for this is called an endoscope and a bundle of optical fibers is in it. Some fibers carry light down and then light reflected and comes back from the other fibers.

Question 35

Why don't messages get mixed up in optical fibers

Answer 35

Multiplexing is the method for sending lots of messages without them getting mixed up

Question 36

What are 2 types of multiplexing

Answer 36

Wavelength division | Time division

Question 37

Multiplexing: wavelength division

Answer 37

Each message sent at different wavelengths and the receiver tunes into the wavelength of the message

Question 38

Multiplexing: time division

Answer 38

Each message is divided into chunks for transmission. Messages are put back at the other end.

Question 39

analogue

Answer 39

a signal with continual varying signals

Question 40

attenuation

Answer 40

loss of strength of a signal during transmission

Question 41

X- rays

Answer 41

form of electromagnetic radiation with very short wavelength and are very high in energy so are strongly ionizing.

Question 42

X-rays wavelength

Answer 42

0.01 to 10nm

Question 43

how are x-rays made

Answer 43

very fast moving electrons are suddenly stopped and where collisions happen when stopped created x-rays and often are created in x-ray tubes

Question 44

stages in taking x-rays

Answer 44

X-ray tube is switched on , x-rays from tube pass through patient’s body. A photographic film or a flat –panel detector is placed on the other side of the patient X-rays pass through soft tissue, but absorbed by bones, teeth and metals objects that are not too thin. The parts of the film or detector panel, where the x-rays get through to, become darker. Therefore, bones, teeth, etc, appear white in comparison. Lead plates between the tube and patient stop x-rays reaching other parts of body. Lead is used as it absorbs x-rays well. A flat- panel detector contains a ‘charge-coupled device’ (CCD). This turns x-rays into light, which in turn create electronic signals, to produce a digital x-ray image.

Question 45

situations of x-ray stages

Answer 45

If the organ being investigated (x-rayed) is made of soft tissue (like the stomach), the x-rays will normally go through it, instead of being absorbed. In that case the organ is filled with a contrast medium – something which will absorb the x-rays so those parts stand out more clearly in a radiograph. E.g. before a stomach x-ray, patient will be given a barium meal – which is good at absorbing x-rays.

Question 46

what safety precautions taken for x-rays: patients

Answer 46

are given as small a dose as possible have radiation targeted only at the area of the body being imaged or treated have other areas protected with a lead shield, which is too dense for X-rays to pass through.

Question 47

what safety precautions taken for x-rays: Radiographers

Answer 47

are high-risk as they are exposed to radiation often wear a lead apron stand behind a screen that absorbs X-rays or even leave the room.

Question 48

Using radiation to treat cancer

Answer 48

Radiotherapy is the use of high-energy ionizing radiation, such as X-rays and gamma rays, to kill cancer cells. In external-beam radiotherapy, a concentrated beam of short-wavelength X-rays or gamma rays (cobalt -60) is targeted at cancerous cells from a radiation source outside the body.

Question 49

Radiotherapy

Answer 49

Gamma rays can kill cancer cells, but are also dangerous to healthy cells We need to target the gamma rays (and high energy x-rays) to the cancer very precisely so that the radiation dose to healthy tissue is kept to a minimum. In particular we need to avoid any nearby organs such as eyes or spinal cord. A medical physicist decides which angles to shine x-rays from to destroy tumour and minimise damage to other tissue

Question 50

how are gamma rays produced

Answer 50

When un unstable nucleus undergoes radioactive decay. Normally an alpha or beta particle is released (with or without EM waves like gamma rays)

Question 51

What are the types of doses

Answer 51

Alpha Beta Gamma

Question 52

Radiation dose

Answer 52

The radiation dose received by a person is a measure of the damage done to their body by ionizing radiation.

Question 53

What does radiation dose depend on

Answer 53

Type of radiation used How long body is exposed to radiation The energy per second absorbed by the body from the radiation.

Question 54

What is radiation dose measured in

Answer 54

Sieverts(SV) and millisieverts(mSV)

Question 55

Dangers of the EM spectrum

Answer 55

the smaller wavelength waves can interact with cells and can be ionising

Question 56

UV radiation from the sun

Answer 56

The Sun emits Ultraviolet (UV) radiation UV waves have enough energy to damage cells Overexposure to UV can cause sunburn or even skin cancer

Question 57

Sunburn and skin cancer

Answer 57

Sunburn is a painful sign that UV is damaging you | Skin cancer is cause by molecules in damaged cells dividing rapidly, forming a tumour

Question 58

Who is at higher Risk from skin cacer

Answer 58

``` are fair skinned and burn quickly have freckles and/or moles were frequently exposed to the sun as children suntan deliberately have a family history of skin cancer work outdoors for long periods of time use solariums, sunlamps and sunbeds. ```

Question 59

Who is less risk of skin cancer

Answer 59

People with darker skins Dark skins contain a pigment called melanin which absorbs UV and prevent it reaching the underlying tissue (live skin cells in body tissues under skin) People with easily tanned skin Weak exposure to UV over a few days can cause fair skins to tan, because the body produces a black pigment called melanin in the skin. People who take steps to protect themselves from UV radiation.

Question 60

How to avoid sunburn

Answer 60

Shade one of the most effective ways to protect against the sun's UV rays Clothing provides a barrier between UV rays and the skin. Hats The correct type of hat shades the face, eyes and neck Sunglasses UV rays can also damage eyes Sunscreen should be the last method of sun protection.

Question 61

Ozone layer

Answer 61

The ozone layer is a layer in Earth’s atmosphere (13-40km up) which contains relatively high concentrations of ozone (O3). This layer absorbs 97–99% of the sun’s high frequency ultraviolet rays, which is potentially damaging to life on earth.

Question 62

How are x-ray produced in x-ray tubes

Answer 62

Electrons from the hot cathode are fired at the tungsten target at high speed. When these high-energy electrons strike the target, some of their energy is changed into X-rays.

Question 63

How x-rays look inside objects

Answer 63

x-rays pass through soft tissue, such as skin and muscle, without being absorbed. Denser tissue, such as bone, can absorb X-rays. Film that is exposed appears black and areas that are not exposed, because of X-ray absorption, are white.

Question 64

Some uses of x-rays

Answer 64

X-rays are used in medicine and in security to check the contents of baggage and vehicles for weapons, drugs and other contraband.

Question 65

X-rays intensity

Answer 65

They loose strength because they are absorbed by denser mediums

Question 66

Unobvious signs of x-ray imagings

Answer 66

Computer Aided Tomography scans (CAT or CT scans) use static X-ray images taken from lots of angles to build up 3D pictures of internal organs. A special type of X-ray imaging machine called a fluoroscope acts as an X-ray video camera. A moving X-ray image of internal organs is shown on a TV screen.

Question 67

What precaution i taken so cells do not get infected by radiotherapy

Answer 67

Radiation is shot from multiple angles

Question 68

Brachytherapy

Answer 68

In brachytherapy, an alpha or beta emitter is surgically implanted into the tumour or a nearby body cavity. This can be used for tumours in sensitive areas, including breast, cervix and prostate cancer.

Question 69

systematic radioisotope therapy

Answer 69

In systematic radioisotope therapy, the isotope is injected into the blood stream. This is used to treat thyroid cancer and to provide palliative care when cancer is advanced.

Question 70

Advantages of external beam therapy

Answer 70

The beam can be moved and targeted at the tumour rather than at surrounding tissue. Effective for tumours in the outer regions of the body. Type of radiation: X-rays or gamma rays. These rays are strongly penetrative and can pass through soft tissues without being absorbed

Question 71

Advantages of internal radiation therapy

Answer 71

For some tumours, brachytherapy can give more intense radiation than external beam radiation, without harming healthy tissue. For example, external beam radiation treatment can cause skin irritation in the area exposed to the beam, which is avoided by internal radiotherapy. Treatment with internal radiotherapy can usually be completed in less time than an equivalent course in external beam radiation, with fewer visits to the hospital for the patient. If the tumour moves in the body, external beam radiation can be miscalculated and fail to target the tumour. However, brachytherapy implants retain their position relative to the tumour. Effective for tumours which are surrounded by sensitive tissue or which are deep within the body so that radiation beams would have to pass through sensitive tissue in order to reach them. Type of radiation: alpha or beta particles. These particles are not very penetrative and are mostly absorbed by tissues surrounding the source of the radiation. This makes them less dangerous for surrounding healthy tissues

Question 72

Disadvantages of external beam therapy and internal radio therapy

Answer 72

Fatigue and nausea are common side effects of all types of radiotherapy. Side effects usually depend on the area treated by radiotherapy and the frequency and intensity of the radiation used.

Question 73

PET imagining

Answer 73

Positron Emission Tomography (PET) is a type of imaging which uses radioactive isotopes. The isotope is injected, swallowed or breathed in. It is called a tracer. The isotope emits positrons through β+ decay, which annihilate electrons inside the body to produce gamma radiation. The scanner detects the gamma rays and creates an image of the body on a screen. Doctors can use this to investigate body functioning, e.g. blood circulation or metabolism.

Question 74

Dose in PET imagining

Answer 74

The isostope is prepared in half-life in the hospital and have a very short period of decay but many hospitals fo not have the equipment for that.