Flashcards in P2 - Radiation and Life Deck (88):
What is the electromagnetic spectrum?
A family of seven radiations, including visible light
What does a beam of electromagnetic radiation contain?
'Packets' of energy called photons
Complete the sentence:
The higher the frequency of an electromagnetic radiation...
...the more energy is transferred by each photon
All electromagnetic radiation travels at the same finite speed of what?
300,000km/s through space (a vaccum)
Name 3 high energy photons, in order from lowest to highest.
Ultraviolet rays, x-rays, gamma rays
Name 3 low-energy photons, in order from lowest to highest.
Radio waves, microwaves, infrared
Name all 7 types of electromagnetic radiation in order from lowest energy photons to highest.
Radio waves, microwaves, infrared rays, visible light, ultraviolet rays, x-rays, gamma rays
The general model of radiation shows how energy travels from a ______ that _____ radiation, to a _______ that ____ radiation.
On the journey from _______ to _______, materials can _______, ____ or _________ radiation.
Give an example of how on the journey from emitter to detector, materials can transmit, reflect or absorb radiation.
Clouds absorb and reflect the Sun's energy, so on a cloudy day, we receive less light than on a clearer day.
Give an example of a) an emitter and b) its detector for radio waves.
a) TV transmitter
b) TV aerial
Give an example of a) an emitter and b) its detector for microwaves.
a) Mobile phone mast
b) Mobile phone
Give an example of a) an emitter and b) its detector for infrared waves.
a) Remote control
Give an example of a) an emitter and b) its detector for light.
a) The Sun
b) The eye
Give an example of a) an emitter and b) its detector for ultraviolet rays.
a) Ultraviolet lamp
b) The skin
Give an example of a) an emitter and b) its detector for x-rays.
a) X-ray machine
b) Photographic plate
Give an example of a) an emitter and b) its detector for gamma rays.
a) Some stars (e.g. supernova)
b) Gamma ray telescope
What is the intensity of electromagnetic radiation?
The energy arriving at a square metre of surface per second
What does intensity of electromagnetic radiation depend on?
The number of photons delivered per second and the amount of energy each packet contains, i.e. the photon energy
a) Does the intensity of a beam increase or decrease with distance?
b) What does this mean?
a) The intensity of a beam decreases with distance
b) The further from a source you are, the lower the intensity.
When a material absorbs radiation, what is created?
When a material absorbs radiation, heat is created. What 2 things does the amount of heat created depend on?
- The intensity of the radiation beam
- The duration of the exposure
a) The decrease in the intensity of radiation with distance is due to what 3 factors? (HT)
b) Why would these factors combine? (HT)
c) What does this result in? (HT)
a) - Photons spread out as they travel
- Some photons are absorbed by particles in the substances they pass through
- Some photons are reflected and scattered by other particles.
b) To reduce the number of photons arriving per second at a detector
c) A lower measured intensity
What is ionising radiation?
Electromagnetic radiation with a high photon energy
What can ionising radiation do?
Break molecules into bits called ions
When molecules are broken into bits by ionising radiation, what are the resultant 'bits' called?
Give some examples of ionising radiation.
- Ultraviolet radiation
- Gamma rays
Are ions unreactive or very reactive? (HT)
Ions are very reactive which means? (HT)
They can easily take part in other chemical reactions
Give 3 ways in which radiation damages living cells.
- The heating effect can damage the skin, e.g. sunburn
- Ionising radiation can age the skin. It can also mutate DNA, which can lead to cancer
- Different amounts of exposure can cause different effects, e.g. high intensity ionising radiation can destroy cells, leading to radiation poisoning.
Give a way that heat radiation can damage the skin.
How do microwaves heat materials?
By causing the water particles to vibrate.
What could there be a health risk from with low intensity microwaves?
Of mobile phones and masts
Microwave ovens have a metal case and a wire screen in the door to do what?
Absorb ultraviolet radiation to help prevent skin cancer
Why do microwave ovens have a metal case and a wire screen in the door to absorb ultraviolet radiation?
To help prevent skin cancer
Give some examples of other physical barriers to protect people from different types of radiation.
- X-ray technicians use lead screens
- Sunscreens and clothing can absorb ultraviolet radiation to help prevent skin cancer
- Nuclear reactors are encased in thick lead and concreate
True or False?
Some radioactive materials emit ionising gamma radiation all the time.
a) What must people going into areas of high radiation wear?
c) What else must they have?
a) A radiation suit
b) As a shield
c) Radiation dose monitor
All objects emit electromagnetic radiation with a _________ _________ that increases with temperature.
All object emit electromagnetic radiation with a principal frequency that ________with temperature.
Does photosynthesis compliment or counteract respiration?
How does photosynthesis counteract respiration?
It removes carbon dioxide and adds oxygen
What is the ozone layer?
A thin layer of gas in the Earth's upper atmosphere.
What does the ozone layer absorb?
Some of the Sun's ultraviolet radiation before it reaches Earth.
What would happen without the ozone layer?
The amount of radiation reaching the Earth would be very harmful. Living organisms, especially animals, would suffer cell damage
What does the energy from ultraviolet radiation cause? (HT)
Chemical changes in the upper atmosphere when it's absorbed by the ozone layer. These
The energy from ultraviolet radiation causes chemical changes in the upper atmosphere when it's absorbed by the ozone layer. Are these changes reversible or irreversible? (HT)
These changes are reversible.
Where does the Earth emit electromagnetic radiation to?
What is in the atmosphere that absorbs radiation, and keeps the earth warmer.
Gases in the atmosphere
What is it known as when gases in the atmosphere absorb radiation, keeping the earth warmer?
The Greenhouse effect
What is the Greenhouse effect?
When gases in the atmosphere absorb radiation, keeping the earth warmer.
How much electromagnetic radiation emitted by the Sun does the atmosphere allow to pass through?
Which greenhouse gas makes up a small amount of the Earth's atmosphere?
Other than carbon dioxide, name some greenhouse gases.
- Water vapour
- Trace amounts of methane
Does radiation emitted by the Earth have a lower or higher principal frequency than that emitted by the Sun? (HT)
Is the carbon cycle an example of a balanced or an unbalanced system?
What does burning forests
b) The number of plants removing CO from the atmosphere
What does burning fossil fuels release?
Carbon that was removed from the atmosphere millions of years ago and had been 'locked up' ever since
For what reason have carbon dioxide levels in the atmosphere been steadily increasing?
Due to human activity, e.g. burning fossil fuels and deforestation
What are decomposers?
Important microorganisms that break down dead material and release CO[2+]
Why have carbon dioxide levels in the Earth's atmosphere remained roughly constant for thousands of years?
Because it was constantly being recycled by plants and animals
How can information (including sound) be transmitted?
What things can be transmitted digitally?
Information (including sound)
How is information transmitted digitally?
The signal is converted into digital code that uses 0 and 1. This is then transmitted as pulses (a series of short bursts of waves). The pulses are decoded to produce a copy of the original sound wave or image.
How are digital pulses read?
0 = no pulse
1 = pulse, i.e. on
How are digital pulses produced?
By switching the electromagnetic carrier wave on and off
What happens when digital signal is received?
The pulses are decoded to produce a copy of the original sound wave or image.
What actually happens when analogue and digital signals become weaker as they travel?
Their amplitude becomes smaller
Why might digital and analogue signals have to be amplified at selected intervals?
Because they become weaker as they travel, meaning their amplitude becomes smaller.
What is the name given to the random variations that digital and analogue signals can pick up?
What is the problem with noise?
It reduces the quality of sound
What happens when a signal is amplified?
Any 'noise' which has been picked up is also amplified
Do digital signals travel longer or shorter distances at a higher quality than analogue signals?
Why do digital signals travel longer distances at a higher quality than analogue signals? (2 reasons)
- Analogue signals can have many different values, so it's hard to distinguish between noise and the original signal. This means that noise can't be completely removed.
- Digital signals only have 2 states, on (1) or off (0), so they can still be recognised despite any noise that's picked up. This means that any interference can be removed.
When digital signals carry noise, it's clear which parts of the signal represent 1 and 0, which means what? (HT)
The signal can be regenerated without the noise.
What is a 'bit'?
One piece of information, represented as either 1 or 0.
What is one byte equal to?
8 'bits' of information.
How is a 'bit' represented?
As either a 1 or a 0.
In a digital mobile phone picture, what does each pixel need?
8 bits of information, or one byte (same thing).
In a digital mobile phone picture, each pixel needs eight bits of information or one byte - the more pixels in the picture... (2 things)
...the more bytes of information there are
...the higher the quality of the picture
a) Where is a digital picture stored on a mobile phone?
b) How is the amount of information stored measured?
a) On a memory card
b) In bytes
What else can be stored in the form of bytes?
Digital music on CDs
How is digital music stored on a CD in bytes?
There is a series of pits, each read by a laser as 1 (a bit), arranged in a spiral on the surface. In between are flat surfaces read as 0. The series of bits is then converted back into analogue form giving a high quality signal.
Give 2 advantages of transmitting information using digital signals.
- Information can be stored, e.g. on hard drive, CD, DVD, or memory stick
- Information can be processed by computer, e.g. for spell checking, photo editing or music editing
Explain 2 ways by which a computer can be used to process and store digital picture information.
- Use of photo editing software to manipulate images
- Store on hard drive, CD, or memory stick
Explain 2 ways by which a computer can be used to process and store music information in MP3/WAV format.
- Remove noise, amplify and edit signals
- Store on hard drive, CD or memory stick
Why is optic fibre useful when sending infrared and light radiation?
They can travel huge distances without becoming significantly weaker