P2- Radiation And Life

Question 1

What is the electromagnetic spectrum?

Answer 1

• Gamma rays
• X Ray’s
• Ultra violet
• Visible light
• Infra red
• Micro waves
• Radio waves

( least harmful)

Question 2

What are photons?

Answer 2

All electromagnetic radiation transfer energy. This energy is delivered as photons.

A photon is a tiny “packet” of energy.

Question 3

Why do some EM radiation transfer energy more than others?

Answer 3

Each photon carries a tiny quantity of energy. But not all photons have the same amount of energy.

The amount of energy carried by a photon depends on the frequency of the radiation.

The frequency and photon energy increases as you go along the spectrum.

Question 4

What is a source?

Answer 4

Many objects emit electromagnetic radiation (Sun, radio transmitter) Any object that emits radiation is called a source.

The frequency of thermal radiation emitted from an object increases with temperature.

Question 5

What is the “speed of light”?

Answer 5

All types of EM radiation can travel through space (a vacuum)

In a vacuum, all EM radiation travels at the same speed- the speed of light.

The speed of light in a vacuum is about 300, 000 km/s.

Question 6

What happens to the radiation from a source?

Answer 6

When radiation is emitted from a source it spreads out until it reaches some matter.

There are a few things that can happen:

• The radiation can be transmitted- just keeps going. (Like light passing through glass)
• It could be reflected- it bounces back (Like light reflected from a mirror)
• The radiation is absorbed- (Like a sunbather absorbing UV rays from the sun)

What happens depends on the type of radiation and how the substance is like. Two or three things happen at the same time. Radiation may be absorbed by objects far away from the source.

Question 7

What are radiation detectors?

Answer 7

Objects that absorb radiation are called detectors. (Like our eyes are light detectors)

Question 8

What happens when radiation is absorbed by a source?

Answer 8

When radiation is absorbed by matter the photons transfer their energy to the matter.

The energy “deposited” by a beam of photons depends on how many photons there are and the energy of each photon.

The intensity of a radiation means how much energy arrives at each square metre of surface per second.

The intensity of a beam of radiation deceases with distance from the source because:

• the beam spreads out
• the beam gets partially absorbed as it travels.

Question 9

What is the equation for total energy?

Answer 9

Total energy= number of photons *energy of each photon

Question 10

What are the units for intensity?

Answer 10

W/m squared

Question 11

How does some EM radiation cause ionisation?

Answer 11

• All substances are made of atoms and molecules.
• When a photon hits an atom or molecule, it sometimes has enough energy to remove an electron and change the atom.
• The changed atoms or molecules can initiate (start) other chemical reactions.
• It takes a lot of energy to remove an electron from an atom or molecule. So only the types of radiation with high enough photon energy can cause ionisation.
• Ultraviolet, X days and gamma rays are called ionising radiation.
• Some substances (radioactive materials) emit ionising gamma radiation all the time.

Question 12

What happens if ionisation happens in your body?

Answer 12

• If your cells are exposed to ionising radiation, the damage done to the DNA molecule can cause mutations. The cells will start dividing over and over without stopping - this is cancer.
• Very high doses of radiation kill your cells- “radiation sickness”.
• UV radiation from the sun can damage living cells and cause sunburn or even skin cancer.
• Increased exposure causes more damage- the longer you are exposed the more damage is done.

Question 13

How to protect from radiation?

Answer 13

UV radiation- physical barriers such as clothes,sunscreen or sun block.

X rays- when an x Ray is taken the parts that aren’t being investigated get covered by lead. The lead absorbs x rays and protects you from getting unnecessary exposure.

Question 14

What does non ionising radiation do?

Answer 14

Non ionising radiation doesn’t have enough energy to change atoms. When it is absorbed by a substance it transfers energy to the atoms or molecules of the substance. And heats them up.

The more intense the radiation and the longer the exposure the greater the heating effect.

This heating effect can damage living cells. However it is also useful as it heats our food.

Question 15

How does a microwave work?

Answer 15

Microwaves make particles vibrate- heating them up. Sometimes microwaves are strongly absorbed by water molecules- so can heat things containing water.

Microwave ovens come in different power ratings. More powerful microwaves produce higher intensity radiation. So less time is needed to produce the same heating effect. Food cooks more quickly.

Microwaves would heat up the water in the body cells if we were exposed to it. Metal cases reflect and absorb the microwaves stopping them from getting out.

Question 16

What are the health risks of microwaves?

Answer 16

Microwaves are used to sent signals between mobile phones and phone masts.

When we make a call on our mobile the phone emits microwave radiation. Some of this radiation gets absorbed by the body and heats up the body’s tissue.

There are concerns of heating of the brain and jaw which could increase the risk of medical conditions such as cancers.
However, no evidence has been found.

The radiation is at a low intensity so the heating would be very minor.

Question 17

How does the greenhouse effect the earths temperature?

Answer 17

The earth absorbs EM radiation from the sun. This warms up the earths surface. The earth then emits some EM radiation back into space- this cools us down.

Most of the radiation emitted from earth is infrared radiation- heat. It is at a lower frequency than most radiation emitted by the sun because the earth is cooler.

The infrared radiation is absorbed by the atmospheric gases. Including carbon dioxide, water vapour, methane.

These gases then re radiate heat in all directions including back towards the earth. The atmosphere acts as an insulating layer by stopping the earth losing heat at night.

This is known as “the greenhouse effect”. Without greenhouse gases (CO2, water vapour and methane) in our atmosphere the earth would be colder than it is now.

However, too much greenhouse gas could lead to global warming.

Question 18

What does the ozone layer do?

Answer 18

Ozone is a form of oxygen. Ozone occurs naturally at a certain height in the atmosphere.- “ozone layer”.

When an ozone molecule (O3) absorbs more UV radiation it splits into O2 and then O. So the reaction is reversible, causing a chemical change each time.

The amount of ozone is constant, but loss of ozone can cause holes in the ozone layer.

Without ozone a lot more UV radiation would reach earth.
UV radiation is ionising and harmful to complex organisms.

So the ozone layer is important because it protects us from too much UV radiation.

Question 19

What is the carbon cycle?

Answer 19

• CO2 and methane keep the earth warm. They are greenhouse gases.
• All the carbon in the earth moves in a big cycle.
• Som processes (mainly respiration) return CO2 to the atmosphere as part of the cycle.
• respiration in plants & animals.
• respiration in decomposers- all plants and animals contain carbon. When they die decomposers (bacteria & fungi) break them down. As they do this they respire and produce CO2.
• Burning trees or coal releases CO2 into the atmosphere.
• Photosynthesis from plants remove CO2 from the atmosphere.
• For thousands of years these processes balanced out. Removal of CO2 and then adding it back. So CO2 has been constant.

Question 20

How are humans affecting the carbon cycle?

Answer 20

Over the past 200 years the concentration of CO2 in the atmosphere has been increasing. CO2 is being released into the air faster then it’s being removed. Here are the reasons;

• People’s lifestyle has changed- we use more electrical gadgets-mor electricity needed- we burn fossil fuels- CO2 released.
• Population is rising-more land needed for food and homes- we chop trees and burn them for space- adds CO2.
• Plants remove CO2 by the process of photosynthesis. Less plants means less CO2 removed from the atmosphere.
• Burning adds more CO2.

Question 21

How does the greenhouse effect lead to global warming?

Answer 21

The global temperature has also increased as the level of CO2 increased.

A lot of evidence shows that rise in CO2 levels is causing global warming by increasing the greenhouse effect.

So there is a scientific consensus (general agreement) that humans are causing global warming.

Global warming is a type of climate change.

Question 22

What are climate models?

Answer 22

Atmosphere, land and oceans all affect each other.

Climate models are a huge amount of equations linking these various parts of the climate system. The idea is a mimic about what goes on in the real climate by doing calculations.

Once you have programmed a big computer with your equations, you need data to start the calculations off. The computer uses the data to work out more information.

We can use climate models to explain why the climate is changing now. Climate models show that natural changes don’t explain “global warming”.

It explains that human activity is increases greenhouse gases.

Question 23

What are the consequences of global warming?

Answer 23

• Sea gets warmer-it expands-causing rise in sea level-low lying places flooded.
• High temperatures-make ice melt-sea levels rise.
• Changed weather patterns- more extreme weather caused.(lightening,storms,hurricanes)
• The extra heat in the atmosphere increases convections. Results in more water vapour. More storms and floods.
• Change in weather patterns-affects food productions-too dry or wet too grow foods.

Question 24

How can EM radiation transmit information?

Answer 24

EM radiation has been used to send information.

• Infrared- TV remote control- “night vision” cameras.
• Microwaves- mobile phones- satellite communication.
• Radio- TV and radio transmitters and radar.

Question 25

What are radio waves mainly used for?

Answer 25

Radio waves and microwaves are good at transmitting information over long distances.

This is because they don’t get absorbed by the earths atmosphere as much as the other EM radiations.

The radio waves used for TV and FM radio transmitters have very short wavelengths compared to most radio waves.

Microwaves used for mobile phone communications have very long wavelengths compared to most microwaves but are still small compared to radio waves.

Question 26

What are microwaves mainly use for?

Answer 26

Communications to and from satellites use microwaves that can pass easily through atmosphere.

For satellite TV the signal from a transmitter is transmitted into space. Where it is absorbed by the satellite receiver dish orbiting the Earth in a different direction.

These dishes are made from metal, metal reflects microwaves.

Question 27

What are optical fibres?

Answer 27

Optical fibres work by bouncing waves off the sides of a thin inner core of glass or plastic.

The wave enters one end of the fibre and its reflected repeatedly until it emerges at the other end.

Light and infrared are the best for transmitting information along optical fibres. The signal doesn’t weaken as it travels along and the glass doesn’t absorb that much radiation.

Question 28

What are analogue and digital signals?

Answer 28

The amplitude or frequency of an analogue signal varies continuously. An analogue signal can take any value in a particular range.

Digital signals can only take one of a small number of discrete values. (On or off)

The information is carried by switching the EM carrier wave on or off. This creates pulses; short bursts of waves.

A digital receiver will decode these pulses to get a copy of the original signal.

Question 29

Why do signals need to be amplified?

Answer 29

Both digital and analogue signals weaken as they travel. So they need to be amplified long their route.

They may pick up some interference or noise from electrical disturbances or other signals.

Question 30

Why are digital signals better quality?

Answer 30

Noise is less of a problem with digital signals than analogue. If you receive a “noisy” digital signal it is obvious what it’s supposed to be.

So the signal is “cleaned up” and the noise doesn’t get amplified.

However, if you receive a noisy analogue signal it is difficult to know what the original would have been. If you amplify a noisy analogue signal you amplify the noise as well.

This is why digital signals are better quality. Another advantage is that you can transmit several signals at once using just one cable or EM wave. So you can send more information than analogue signals.

Digital signals are easy to process using computers. As computers are digital devices.

Question 31

What are digital signals measured in?

Answer 31

The amount of information used to store a digital image or sound is measured in bytes.

Images and sounds will be of higher quality when the amount of information stored is higher.

Question 32

What is radiation?

Answer 32

It is a transfer of energy.

Visible light is radiation that our eyes can detect.