P2 - Radiation and life Flashcards
What is light a type of?
A type of Electromagnetic Radiation (EM radiation).
You only see things only when your eyes (detectors) absorb what?
The Electromagnetic radiation (i.e. light)
Some of the things that we see are called what?
What do they emit? How do they emit this?
Some of the things that we see are LIGHT SOURCES.
They EMIT LIGHT, often by GLOWING HOT.
Everything else that we see ____ light.
REFLECTS
Black objects don’t reflect much light, they mostly _____ it.
ABSORBS
Light is one part of the ____________.
ELECTROMAGNETIC SPECTRUM
All waves in the electromagnetic spectrum ______ through a _____ at 300 000 km/s.
All waves in the electromagnetic spectrum TRANSMIT through a VACUUM at 300 000 km/s.
The energy of a waves in the spectrum increases with…..?
Increasing frequency
Waves with higher frequencies carry…?
MORE energy
What are photons?
Packets of energy that electromagnetic waves transfer.
The energy in a photon depends only on the….
Frequency of the wave.
Increasing the frequency of an electromagnetic wave…
increases the energy of its photons.
What is the order of the electromagnetic spectrum?
RADIO WAVES, MICROWAVES, INFRARED, VISIBLE LIGHT, ULTRAVIOLET, X-RAYS, GAMMA RAYS
Increases Frequency, Decreases Wavelength
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The energy absorbed in each second from an electromagnetic wave depends on its _____
INTENSITY
What two things do intensity depend on?
- The number of photons per second (intensity increases with number of photons)
- The energy transferred by each photon (intensity increases with energy).
The energy of a wave is spread over an increasing area as it…
…moves away from its source.
The intensity of the wave decreases with ____ distance from its source
The intensity of the wave decreases with increasing distance from its source
The intensity of an EM wave is the…
…energy transferred to each SQUARE METRE of absorbing surface in EACH SECOND.
What are the units of intensity?
J / m^2 / s
The intensity of a wave in a vacuum is ___________ to the ____ of its distance from its source.
The intensity of a wave in a vacuum is INVERSELY PROPORTIONAL to the SQUARE of its distance from its source.
If the wave is partially absorbed by the medium it is passing through, the….
…intensity drops even more rapidly than an inverse square law.
What happens in ionisation?
When a photon hits an atom or a molecule, it sometimes has enough energy to REMOVE AN ELECTRON and change the atom or molecule, which can initiate other chemical reactions.
What are the only three ionising radiations in the EM spectrum?
- high energy ULTRAVIOLET
- X-rays
- Gamma Rays
Radioactive materials emit…
GAMMA rays.
Gamma rays pass…
easily through the human body.
X-rays pass through…
muscle but are ABSORBED by the bone.
When cells absorb gamma rays or X-rays what happens to them?
They become ionised and damaged.
What can the damaged cells either do?
DIE or DEVELOP INTO CANCER.
Why are X-rays used to make shadow pictures of people’s bones or their luggage?
Because X-rays are absorbed by dense materials.
How do radiographers in hospitals protect from the ionising radiation?
By LEAD and CONCRETE screens.
Things which absorb radiation….
HEAT UP.
Cells which absorb radiation are….
damaged if they get too hot.
You can increase the thermal energy transferred from radiation by doing what?
Increasing its exposure time and intensity.
Why are microwaves good to heat objects containing water?
Microwaves are strongly absorbed by water molecules.
How do microwaves protect people from the radiation?
Microwaves inside the machine reflect off the metal in the walls and door or are absorbed by them instead of escaping.
Mobile phone networks use _______________.
LOW INTENSITY microwaves.
How is the risk of cell damage from mobile phones measured?
By comparing cancer rates in large groups of people who do and do not use mobile phones.
Sunlight contains….
ULTRAVIOLET radiation.
Ultraviolet radiation can cause:
Sunburn and skin cancer.
What 2 things can protect people? How do they protect them?
Sunscreens and clothings.
They absorb UV radiation emitted by the Sun.
What is Ozone (O3) ?
A layer at the top of the atmosphere that absorbs UV radiation from the Sun. This protects living things on Earth from some of the harmful effects of UV radiation.
Increased exposure to UV radiation can increase the risk of?
developing SKIN cancer
If the ozone layer thins by 1%, the risk of skin cancer increases by about…
4%
UV radiation from the Sun causes what?
Chemical changes to molecules in the ozone layer.
How does the Earth warm up?
When it absorbs radiation from the Sun.
What does the Earth do to cool itself down?
Emits Infrared radiation which can either pass into space, reflect off clouds, or radiate back from gases which absorb it.
When the Earth’s radiation is absorbed or reflected back, this keeps the Earth warmer. This is called the…
GREENHOUSE EFFECT.
Everything emits some EM radiation with a…
RANGE of frequencies
The PRINCIPAL FREQUENCY of that radiation is…
the one with greatest intensity.
