P1 - Radiation & Waves Flashcards
List the order of the electromagnetic
spectrum in order of increasing
wavelength
List the order of the electromagnetic spectrum in
order of increasing wavelength
Gamma, X Ray, UV, Visible, Infrared,
Microwaves, Radio
What is the highest frequency
electromagnetic wave?
What is the highest frequency electromagnetic
wave?
Gamma waves
What is the highest energy
electromagnetic wave?
What is the highest energy electromagnetic wave?
Gamma waves
What properties are shared by all
electromagnetic waves?
What properties are shared by all electromagnetic waves? ● They are all transverse waves ● They all travel at the same speed (3x10⁸ m/s) ● They can travel through a vacuum
A wave transmits energy from…
A wave transmits energy from…
…source to absorber.
e.g. from a light source to the eye
What range of frequencies of
electromagnetic waves can be detected
by the human eye?
What range of frequencies of electromagnetic waves
can be detected by the human eye?
400-700 nanometres
What can happen when radiation strikes
an object?
What can happen when radiation strikes an object? It can be… ● transmitted ● reflected ● absorbed
When low energy radiation is absorbed,
it usually causes…
When low energy radiation is absorbed by an object,
it usually causes…
Heating
When high energy radiation is absorbed,
it can lead to…
When high energy radiation is absorbed, it can lead
to…
Ionisation (the removal of electrons from
atoms/molecules).
How are electrons arranged in atoms?
How are electrons arranged in atoms?
Electrons are found in ‘energy levels’ or
‘shells’ at different distances from the
nucleus.
How does electromagnetic radiation
affect electron arrangement in atoms?
How does electromagnetic radiation affect electron
arrangement in atoms?
Absorption or emission of electromagnetic radiation can cause electron arrangement to change. (It can
remove electrons from the atom or move electrons further from the nucleus).
How do atoms become ions?
How do atoms become ions?
By losing an outer electron.
What are the effects of body cells
absorbing radiation?
What are the effects of body cells absorbing
radiation?
Large amounts can damage cells.
Smaller amounts cause mutation,
causing cells to divide rapidly, which can
lead to cancer.
Gamma rays are emitted from…
Gamma rays are emitted from…
The nuclei of atoms.
What is emitted when electrons in atoms
lose energy?
What is emitted when electrons in atoms lose
energy?
X rays, UV and visible light
What types of radiation can cause
ionisation?
What types of radiation can cause ionisation?
Gamma, X-rays and high energy UV (as
these have sufficient energy).
Atmospheric oxygen interacts with
ultraviolet radiation to produce…
Atmospheric oxygen interacts with ultraviolet
radiation to produce…
Ozone.
Describe the function of atmospheric
ozone.
Describe the function of atmospheric ozone.
Ozone absorbs UV radiation from the sun, protecting the Earth and living organisms from harmful rays.
How does infrared radiation interact with
molecules?
How does infrared radiation interact with molecules?
It is emitted and absorbed by molecules.
How does UV radiation affect body
tissue?
How does UV radiation affect body tissue?
UV radiation can cause cancer when skin is exposed to it.
It can cause blindness if eyes are
overexposed to UV radiation.
How do X-rays affect body tissue?
How do X-rays affect body tissue?
X-rays are ionising so they can damage or kill cells and cause mutations that could lead to cancer.
How do gamma rays affect body tissue?
How do gamma rays affect body tissue?
Gamma rays are even more ionising than X-rays, so they can cause cell mutations (which can lead to cancer) and cell death.
How are radio waves produced?
How are radio waves produced?
When there is an oscillating current in an
electrical circuit.
How are radio waves detected?
How are radio waves detected?
When the waves cause an oscillating
current in a conductor.
State and explain a use of radio waves
State a use of radio waves
Communications, because radio waves are long wavelength and can travel long distances without losing quality.
State and explain a use of microwaves
State and explain a use of microwaves
Cooking, as microwaves are absorbed
by and heat fat/water in foods.
State and explain uses of infrared
radiation
State and explain uses of infrared radiation
Cooking food (as it transfers thermal energy) infrared cameras, short range communication.
State and explain uses of visible
radiation
State and explain uses of infrared radiation
Illuminating (i.e. seeing) and fibre optics,
as they reflect best in glass (other waves
have wavelengths that are too
long/short).
State and explain uses of UV radiation
State and explain uses of UV radiation
Sterilisation, as it kills bacteria, energy
efficient lamps, as it radiates low heat
but high energy, and sun tanning etc.
State and explain uses of X rays
State and explain uses of X rays
Medical imaging and treatment, because
they are very high energy and can easily
penetrate body tissues.
State and explain uses of gamma rays
State and explain uses of gamma rays
Gamma rays are used in medical
treatments, such as radiotherapy in the
treatment of cancer.
What objects emit electromagnetic
radiation?
What objects emit electromagnetic radiation?
All objects emit electromagnetic radiation of a principle frequency; the principle frequency of emitted radiation increases with temperature.
How does the temperature of an object
affect the EM radiation emitted?
How does temperature of an object affect the
radiation emitted by an object?
● The amount (intensity/power) of radiation
emitted per second increases as
temperature increases.
● The type of radiation changes; the hotter the
body the shorter the wavelength of radiation
released (eg. X rays and gamma rays).
A body with constant temperature…
A body with constant temperature…
Emits radiation at the same rate as it
absorbs it.
How do objects increase or decrease in
temperature?
How do objects increase or decrease in
temperature?
● If an object emits energy at a higher rate
than it absorbs, it will decrease in
temperature.
● If an object absorbs energy at a higher rate
than it emits, it will increase in temperature.
How does the Earth’s atmosphere affect
radiation?
How does the Earth’s atmosphere affect radiation?
The atmosphere largely absorbs or reflects radiation from the sun, preventing it from reaching Earth. Some
radiation, however, is allowed to pass through and warms the earth.
How is radiation emitted from the Earth
different to radiation emitted by the sun?
How does the radiation emitted from the Earth differ
from the radiation emitted by the sun?
It has a lower principle frequency.
What happens to the radiation emitted
from the Earth?
What happens to the radiation emitted from the
Earth?
It is absorbed and re-emitted in all directions by greenhouse gases, resulting in the greenhouse effect which warms the earth.
Give 3 examples of greenhouse gases in
Earth’s atmosphere
Give 3 examples of greenhouse gases in Earth’s atmosphere ● carbon dioxide ● methane ● water vapour
Explain why carbon dioxide levels have
increased over the past 200 years
Explain why carbon dioxide levels have increased over the past 200 years ● Burning fossil fuels (increases CO2 output). ● Deforestation (decreases CO2 absorbed by trees).
What is a wave?
What is a wave?
A regular disturbance that transfers
energy in the direction the wave is
travelling without transferring matter.
What is a transverse wave?
What is a transverse wave?
A wave in with oscillations that are at
right angles (perpendicular) to the
direction of motion.
Give examples of transverse waves
Give examples of transverse waves
Waves on a string, all electromagnetic
waves (eg. visible light), ripples on water,
vibrations on guitar strings.
What is a longitudinal wave?
What is a longitudinal wave?
A wave in which the disturbances are parallel to (in the same direction as) the direction of motion.
Give examples of longitudinal waves
Give examples of longitudinal waves
Pulses along a spring, sound waves, ultrasound.
Transverse waveforms have…
Transverse waveforms have…
Peaks and troughs
Longitudinal waveforms have…
Longitudinal waveforms have…
Compressions and rarefactions
Wavelength is…
Wavelength is…
The shortest distance between the same point on two consecutive waves (e.g. the distance between two consecutive peaks/troughs/compressions/rarefactions).
Displacement is…
Displacement is…
The distance from equilibrium position.
When displacement is at a maximum
(peaks/troughs), this is the amplitude.
Frequency is…
Frequency is... The number of complete waves passing a point per second (or the number of waves produced by the source per second).
Period is…
Period is…
The time taken for a whole wave to pass
through a single point.
State the wave equation
State the wave equation v = λ x f ● v = velocity (m/s) ● λ = wavelength (m) ● f = frequency (Hz)
Give an equation relating time period
and frequency.
Give an equation relating time period and frequency T = 1/f f = 1/T ● T = time period (s) ● f = frequency (Hz) The two quantities are reciprocals of each other.
What is a ripple tank?
What is a ripple tank? A shallow glass tank with an oscillating paddle/needle to create waves. It is illuminated from above so the waves can be seen on the surface below the tank.
Describe how to measure the speed of
water waves using a ripple tank
Describe how to measure the speed of water waves
using a ripple tank
● Set up ripple tank with a motor, power supply, meter ruler and approx. 5cm deep water.
● Adjust the frequency of the motor so low frequency waves can be observed.
● Measure the length of 5 waves using a ruler (the more waves measured the better) and divide by the number of waves to calculate the wavelength of one
wave.
● Count the number of waves passing a point in 10 seconds and divide by 10 to get the frequency.
● Use v=λf to calculate speed.
Describe a procedure to measure the
speed of sound waves in air
Describe a procedure to calculate the speed of
sound in air
● Place 2 people 100m apart, person 1 with a starting
pistol and 2 with a stopwatch.
● Person 1 will fire a starting pistol and raise their hand at the same time.
● Person 2 should start the stopwatch when they see the hand raised and stop it when they hear the gun fired.
● Speed = distance (100m) ÷ time.
What is refraction?
What is refraction?
Refraction is the change in speed of a wave as it reaches a boundary between two media, usually resulting in a change in direction (if it enters at an angle).
What property of a wave is not changed
by refraction?
Which property of a wave is not changed by
refraction?
The frequency
Why is frequency not altered by
refraction?
Why is frequency not altered by refraction?
Energy must be conserved
(conservation of energy) so frequency
remains constant.
What happens when waves are incident
on a flat surface?
What happens when waves are incident on a flat
surface?
Reflection.
A stronger reflected wave is produced
when…
A stronger reflected wave is produced when…
The surface is smoother.
Why do rough surfaces appear matt
when illuminated?
Why do rough surfaces appear matt when
illuminated?
The reflected light is scattered in all
directions.
When entering a denser material, light
waves…
When entering a denser material, light waves…
…slow down and bend towards the
normal.
When entering a less dense material,
light waves…
When entering a less dense material, light waves…
…speed up and bend away from the
normal.
How does wavelength affect refraction?
How does wavelength affect refraction?
Shorter wavelength waves refract more.
What happens when white light is shone
through a prism?
What happens when white light is shone through a
prism?
It separates into a spectrum of all its
coloured light components.
Why is white light separated by a prism?
Why is white light separated by a prism?
Each different coloured light wave has a different wavelength. The shortest wavelength light (blue) refracts the most while longer wavelengths (red) refract
more, producing a spectrum.
How can refraction be measured?
How can refraction be measured?
The angle of incidence, i, and angle of refraction, r, can be measured and compared. All angles are measured
relative to the normal.
When light is reflected, how do angles i
and r compare?
When light is reflected how do angles i and r
compare?
angle of incidence = angle of reflection
What are the two types of reflection?
What are the two types of reflection?
Specular and diffuse reflection.
Define specular reflection
Define specular reflection
Reflection off smooth surfaces (such as mirrors) in a single beam which makes the same angle with the normal as the incident beam.
Define diffuse reflection
Define diffuse reflection
Reflection off a rough surface, resulting
in scattering of light.
Define transmission
Define transmission
The process of waves passing through a
transparent material and emerging from
the other side.
Define absorption
Define absorption
When the energy of a wave is taken in
by a surface.
Explain how absorption occurs
Explain how absorption occurs When the frequency of light matches the energy levels of electrons, the light is absorbed by electrons and re-emitted over time as heat.
Why do some objects appear white?
Why do some objects appear white?
Objects appear white when it scatters all colours of light that are incident upon it.
Why do some objects appear black?
Why do some objects appear black?
Objects appear black when they scatter
none of the light incident upon them; in
other words, they absorb all light.
Explain why objects appear coloured
e.g. green
Explain why objects appear coloured (e.g. green)
An object appears coloured when it absorbs some wavelengths and reflects others. A green object appears green because green light is reflected.
When light passes through a concave
lens…
When light passes through a concave lens…
The light rays bend away from the
normal.
When light passes through a convex
lens…
When light passes through a convex lens…
The light rays bend towards the normal,
and meet at a focal point.
What is the principal focus of a lens?
What is the principal focus of a lens?
A focal point before a convex lens, from
which the light rays appear to come from, or the focal point after a concave lens where all the rays meet.
What is a virtual image?
What is a virtual image?
An image produced on the same side of
the lens as the object.
A virtual image cannot be formed on a
screen as the light rays never cross after
the lens.
What is a real image?
What is a real image?
An image produced on the opposite side
of the lens from the object.
A real image can be formed on a screen
as the light rays cross after the lens.
Check for lens diagrams
k
Give an example of a use of concave
lenses
Give an example of a use of concave lenses
Glasses to correct short-sightedness
Give examples of uses of convex lenses
Give examples of uses of convex lenses
● Magnifying glasses
● Binoculars
● Glasses to correct long-sightedness
How does sound travel through solids?
How does sound travel through solids?
Sound waves cause vibrations through
the solid.
Describe the function of the outer ear
Describe the function of the outer ear
The outer ear collects sounds and
channels them down the ear canal.
What happens when sound waves hit the
eardrum?
What happens when sound waves hit the eardrum?
(Higher)
● The taut membrane vibrates as the pressure
waves reach it.
● The eardrum is forced in by compression and
out by rarefaction.
● The eardrum vibrates at the same frequency
as the sound waves.
What is the purpose of the stirrup
bones?
What is the purpose of the stirrup bones?
They vibrate at the same frequency as
the eardrum, and transmit the vibrations
to the inner ear fluid, amplifying the
sound waves received by the eardrum.
What is the cochlea?
What is the cochlea?
A spiral shaped cavity in the inner ear
involved in hearing.
How are sounds conveyed to the brain?
How are sounds conveyed to the brain?
● As the cochlear fluid moves, small hairs which
line it are also moved.
● Each hair moves according to a specific
frequency, and each one is connected to a nerve
cell.
● When a certain threshold frequency is reached,
an electrical impulse is sent to the brain.
What is the frequency range of human
hearing?
What is the frequency range of human hearing?
20-20000Hz (we are incapable of
hearing sounds below 20Hz or above
20kHz).
Through what medium does sound travel
best?
Through what medium does sound travel best?
Sound travels best in solids and worst in
gases, because it relies on particle
collisions. In solids, the arrangement of
particles is most dense, resulting in more
collisions.
What is the optimum range of human
hearing and why?
What is the optimum range of human hearing and
why?
1kHz-3kHz, because this is the range of
frequencies most efficiently transmitted
by the stirrup bones.
How and why can human hearing
deteriorate?
How and why can human hearing deteriorate?
● Constant loud noise damages cochlear hairs ● Smoking ● Chemotherapy ● Diabetes ● age
Define ultrasound
Define ultrasound
Sound waves with frequencies above
20kHz.
How can ultrasound be used to measure
distances?
How can ultrasound be used to measure distances?
● When waves reach a boundary between two media, they are partially reflected.
● The speed of the waves is constant.
● The time between emission and detection can be used to calculate distance (from distance = speed x time). (remember to halve the time; the recorded time is for the distance there and back)
Describe applications of ultrasound
Describe applications of ultrasound Ultrasound is used largely in medical imaging, specifically pregnancy scanning, as it is non-ionising so it does not increase the risk of cancer.
What is SONAR imaging?
What is SONAR imaging? SONAR (Sound Navigation and Ranging) uses both low and high frequency sound waves for imaging eg. underwater.
What is infrasound?
What is infrasound?
Infrasound uses sound waves with
frequencies lower than 20Hz (aka
seismic waves).
Describe two types of seismic waves
Describe two types of seismic wave P waves - longitudinal and can pass through solids and liquids. S waves - transverse, slow moving and can only pass through solids.
What is infrasound used for?
What is infrasound used for?
Infrasound is used to study the structure
of the Earth.
How does infrasound provide evidence
for the Earth’s structure?
How does infrasound provide evidence for the Earth’s structure? Only P waves are detected across the Earth from an earthquake; the lack of S waves implies that the Earth’s core is liquid as S waves cannot penetrate it.
