topic 6 Flashcards
what is the effect of each type of radiation based on
how much energy the wave transfers
what happens when low frequency waves pass through soft tissue
they don’t transfer much energy and so mostly pass through soft tissue without being absorbed
why are high frequency waves dangerous
because they all transfer lots of energy and so can cause lots of damage
what is UV radiation damaging to
-surface cells, which can lead to sunburn and cause skin to age prematurely
what are the serious effects of uv radiation
it can cause blindness and an increased risk of skin cancer
give 2 examples of ionising radiation
gamma rays and X-rays
gamma and x-rays carry enough energy to do what …
knock electrons off of atoms
how is ionising radiation dangerous
it can cause gene mutation, cell destruction or even cancer
what is radiation dose measured in
sieverts
what is radiation dose
a measure of the risk of harm from the body being exposed to radiation
what does the risk of radiation dose depend on
the total amount of radiation absorbed and how harmful the type of radiation is
what are optic fibres
thin glass or plastic fibres that can carry data from telephones or computers over long distances as pulses of visible light
how do optic fibres transmit data
by using visible light
how does light rays work by
reflection- the light rays are bounced back and forth until they reach the end of the fibre
why is visible light used in optic fibres
because it is easy to refract light enough so that it remains in a narrow fibre
how do you get a clearer x-ray image, what does it depend on
it depends on the amount of x-ray radiation that is absorbed through the body
what is x-rays and gamma rays used to treat
cancer
what can gamma radiation also be used as
a medical tracer- this is where a gamma-emitting source is injected into the patient, and its progress is followed around the body
how do radiographers keep safe from x-ray and gamma radiation
they stand behind a lead screen, wear lead aprons or leave the room
what do fluorescence light generate and what is it re-emitted as
UV radiation- which is absorbed and re-emitted as visible light by a layer of phosphorus on the inside of a bulb
why are fluorescence lights good
because they are energy-efficient and and can be used when light is needed for a long period of time
what can security pens used to do
used to mark properties with names and can only glow under UV light
what is uv radiation produced by
the sun
what does communication to and from satellites use
microwaves
if you want to use microwaves for communication what do the microwaves need to pass through
the earth’s watery atmosphere
in microwave ovens what do the microwaves need to be absorbed by
water molecules in the food
absorbing IR radiation causes objects to what …
become hotter
what can IR radiation be used for
-cameras to see detect houses or objects and electric heaters
what are EM waves made up of
oscillating electric and magnetic fields
what type of current is made up of oscillating charges
alternating currents
as charges oscillate, what do they produce
oscillating electric and magnetic fields or electromagnetic fields
what are radio waves mostly used for
communication
when waves travel through a medium what happens to the particles
the particles of the medium oscillate and transfer energy between each other
what is the wavelength
the distance between the trough of one wave and the trough of wave next to it
what is the frequency
the number of complete waves passing a certain point per second
describe the oscillations in transverse waves
they are perpendicular (at 90 degree angles) to the direction of energy transfer
give 3 examples of transverse waves
- all electromagnetic waves
- ripples and waves in water
- a wave on a string
describe the oscillations in longitudinal waves
the oscillations are parallel to the direction of energy transfer
give an example of a longitudinal wave
a sound wave in the air
name the 3 things that can happen when a wave meets a boundary between 2 materials
1) the wave is ABSORBED by the second material
2) the wave is TRANSMITTED through the second material
3) the wave is REFLECTED
electromagnetic waves are what type of waves
transverse waves
what are electromagnetic waves vibrations of
electric and magnetic fields , this means that they can travel through a vacuum (space)
from the start of the EM wave spectrum, describe the frequency and the wavelength
it has a long wavelength and low frequency
at the end of the EM wave spectrum, describe the frequency and the wavelength
it has a short wavelength and high frequency
what is refraction
when waves hit a boundary at an angle and change direction
what happens when a wave crosses boundary between 2 materials
it changes speed
what is the optical density of a material
a measure of how quickly light can travel through a material
what is wave speed
the speed at which the wave moves through the medium (i.e. the speed at which energy is transferred)
1Hz=
1 wave per second
wave speed (m/s)=
frequency (Hz) X wave length (m)
how can we make sure that the results are accurate for reaction times (3)
- take results and remove any results that are anomalous -calculate mean value
- more people with timers
how can we reduce the problem of pressing the timer at correct times
by increasing the distance between the 2 people
what happens to waves when they change direction
it changes speed
when light passes from air into glass what happens
the velocity of light decreases (the light waves slow down.)
this causes the direction of the wave to change
when waves slow down they …
bend towards the normal
what happens when …
waves pass from the glass back to the air
their velocity increases- the light waves speed up
what happens when waves speed up
they bend away from the normal
when can refraction happen
when any wave changes speed as it passes from one medium to another
