P6- Waves Flashcards
What does a wave transfer
Energy from one place to another
What causes a wave
A vibration
What is the definition of a transverse
The vibration causing a transverse wave is perpendicular to the direction of travel wave is parallel
What is the definition of a longitudinal wave
The vibration causing a longitudinal wave is parallel to the direction of travel of the wave
Give three examples of longitudinal waves
Sound, ultrasound and primary earthquake (p) waves
Give three examples of transverse waves
Water waves, all Em waves and secondary earthquake(s) waves
What is a compression
A compression is when particles in a longitudinal wave are closest together
What is a rarefaction
A rarefaction is when particles in a longitudinal wave are furthest apart
What is the amplitude
The amplitude is the maximum displacement of a wave from its equilibrium position
What is the wavelength
The distance from a point on one wave to the same point on the next wave
What is the frequency
The number of waves passing a point each second
What are the units of wave speed, wavelength and frequency
Wave speed-m/s, wavelength-m, frequency - Hz
What is the wave speed equation
v= f x λ Speed = Wavelength x Frequency
What speed do EM waves travel at
300 000 000 m/s
What speed does sound travel at
330 m/s
List the EM waves in order from longest to shortest wavelength
Radio, microwave, infra-red, visible, ultra-violet, x-ray, gamma
Which EM wave has the highest frequency
Gamma
which EM wave has the most energy
Gamma
Which three EM waves are ionising
Ultra-violet, x-ray and gamma
What happens when light travels from air into a glass block
It refracts towards the normal as glass is more dense than air
What happens when light travels from a glass block into air
It refracts away from the normal as air is less dense than glass
What is the law of reflection
The angle if incidence is equal to the angle of reflection
What is the danger of ultra-violet light
Can cause skin to age prematurely and increase the risk of skin cancer
What is the danger of X-rays and gamma ray
X- rays and gamma rays are ionising radiation that can cause the mutation of genes and cancer
What are radio waves used for
Television and radio transmission
What are microwaves use for
Satellite communication ( as they can travel through ionosphere) and for cooking food
What is infra-red used for
Electrical heaters, cooking food and infrared cameras
What is visible light used for
Fibre optic communications (and our vision)
What is ultra-violet used for
energy efficient lamps, sun tanning
What are X-rays used for
Medical imaging and security scanning
What are gamma rays used for
Medical treatment (radiotherapy)
What is the equation for time (waves)
1 ÷ f (Hz)
What are the two types of waves?
- Transverse
2. Longitudinal
What is a transverse wave?
A wave for which the oscillations are
perpendicular to the direction of energy
transfer.
What is a longitudinal wave?
A wave for which the oscillations are
parallel to the direction of energy
transfer.
Give two examples of transverse waves.
- Electromagnetic waves
2. Seismic s-waves
Give two examples of longitudinal waves.
- Sound waves
2. Seismic p-waves
What are the two parts of a longitudinal wave called?
Compressions and rarefactions.
What is a wave’s amplitude?
The maximum displacement of a point
on a wave from its undisturbed position.
What is wavelength?
● The distance from a point on a wave to the same position on the adjacent wave ● Most commonly peak to peak or trough to trough
What is the frequency of a wave?
The number of waves that pass a given
point each second.
What is the unit used for frequency?
Hertz, Hz
What is meant by a frequency of 200Hz?
200 waves pass a given point each
second
What is wave speed?
The speed at which the wave moves or
at which energy is transferred through a
medium.
What does a wave transfer?
Energy
State the equation used to calculate wave speed.
Give appropriate units.
Wave Speed = Frequency x Wavelength
Speed (m/s), Frequency (Hz),
Wavelength (m)
What word is used to describe when a wave
bounces off a surface?
Reflection
How do sound waves travel through a solid?
The particles in the solid vibrate and
transfer kinetic energy through the
material.
What is the frequency range of human hearing?
20 Hz - 20kHz
1kHz = 1000 Hz
What are ultrasound waves?
Waves which have a frequency higher
than the upper limit of human hearing
(20kHz)
Give an example use for ultrasound waves?
Medical or industrial imaging.
What natural event causes seismic waves to be
produced? What types are produced?
● Earthquakes
● They produce both P-waves and
S-waves
State a difference between the mediums that
P-waves and S-waves can travel through.
● P-waves travel through both solids and
liquids
● S-waves only travel through solids
(not liquids)
What technique is used to detect objects in deep
water and measure water depth?
● Echo sounding
● High frequency sound waves are emitted,
reflected and detected
● Time difference between emission and detection,
alongside wave speed, are used to calculate
distances
What type of spectrum do electromagnetic waves
form?
A continuous spectrum.
Order the types of electromagnetic radiation from
lowest to highest frequency.
● Radio waves ● Microwaves ● Infrared ● Visible Light ● Ultraviolet ● X-rays ● Gamma Rays
How do the speeds of EM radiation differ in a
vacuum and in air?
Electromagnetic waves all travel at the
same speed in a vacuum and in air
What property of waves in different mediums causes
refraction?
● Velocity
● Wave speed is slower in denser
materials, causing refraction
In which direction (relative to the normal) do waves
refract when entering a denser medium?
● They bend towards the normal
● The angle of refraction is less than the
angle of incidence
What type of waves can be produced by oscillations
in an electrical circuit?
Radio waves.
How can radio waves create an alternating current in
a circuit?
When radio waves are absorbed, they
can induce oscillations in a circuit with
the same frequency as the waves
themselves.
Where do gamma rays originate from
They originate from changes in the
nuclei of atoms.
What health effects can ultraviolet waves cause
● They can cause the skin to age
prematurely
● The can increase the risk of
developing skin cancer
What health effects can X-rays and Gamma rays
cause
● They are ionising radiation so can
cause mutations in genes
● They can lead to increased risk of
developing various cancers
Give three practical uses for infrared radiation
- Electrical heaters
- Cooking food
- Infrared cameras
Give two practical uses for microwave radiation
- Satellite communications
2. Cooking food
Give two practical uses for radio waves
- Television transmission
2. Radio transmission
What wave phenomenon is used by lenses to form
an image?
Refraction.
How does a convex lens form an image?
Parallel rays of light are refracted and
brought together at a point known as the
principal focus.
What is meant by the focal length of a lens?
The distance from the lens to the
principal focus
What is the difference between the image produced
by a convex and a concave lens?
● Convex lenses can produce real or
virtual images
● Concave lenses can only produce
virtual images
Why does magnification not have a unit?
● It is the ratio between image height
and object height
● Ratios do not require units
What determines the colour of visible light waves
The wavelength and frequency of the
light waves.
What colour of visible light has the highest
frequency?
Blue
What colour of visible light has the largest
wavelength?
Red
What is meant by the term ‘specular reflection’
Reflection from a smooth surface in a
single direction.
What is meant by the term ‘diffuse reflection’?
Reflection from a rough surface which
causes scattering.
How does a red colour filter work?
● A red filter absorbs all wavelengths of light other than those in the red range of the spectrum ● This means only red light passes through the filter
What determines the colour of an opaque object
● Different objects reflect different wavelengths of light by different amounts ● The wavelengths that are most strongly reflected determine the colour
What happens to the wavelengths of light that aren’t
reflected by an opaque object?
Any wavelengths that aren’t reflected are
absorbed by the object.
What colour does an object appear if all wavelengths
are reflected by equal amounts
White
What colour does an object appear if all wavelengths
are absorbed?
Black
What do all bodies (objects) emit and absorb?
Infrared radiation
What happens to the quantity of infrared radiation
emitted by an object as temperature increases?
The hotter the object, the more infrared
radiation it will emit.
What is a perfect black body
An object that absorbs all of the radiation
that is incident upon it.
How much radiation does a perfect black body
reflect or transmit
None.
Why is a perfect black body the best possible emitter
of radiation?
● It is a perfect absorber since it absorbs
all radiation incident on it
● A perfect absorber is also a perfect
emitter
Other than the intensity of radiation emitted, how
does increasing the temperature of an object affect
its emissions?
The wavelength distribution of any
emission is dependent on the object’s
temperature.
What can be said about the rates of emission and
absorption for a body at constant temperature
The body is absorbing and emitting
radiation at the same rate
What can be said about the rates of emission and
absorption for a body increasing in temperature
The body is absorbing radiation faster
than it is emitting it
Give two factors that affect the temperature of the
Earth.
- The Earth’s rate of absorption and
emission of radiation - The amount of reflection of radiation
into space
Define a perfect black body
An object that absorbs al of the radiation that hits it
A white star expands and its surface appears redder in colour. Describe how the surface temperature of the star has changed
The radiation emitted covers a large range of wavelengths
Electromagnetic radiation from the Sun affects the temperature of the Earth. Explain, with respect to the radiation emitted by the Sun and Earth, how the temperature of the Earth remains approximately constant (6)
○ During the day, the half of the Earth which is facing the Sun is hit by radiation emitted by the sun
○ Some of this radiation is absorbed by the atmosphere and the Earth’s surface
○ Because of this, the amount of radiation absorbed during the day is greater than the amount that is emitted
○ This causes an increase in local temperature
○ The half of the Earth which is facing away from the Sun has no radiation from the Sun hitting it - it is night time.
○ This half of the Earth absorbs very little radiation but emits radiation at its usual rate
○ So at night time radiation is emitted at a much higher rate than it is absorbed.
○ This causes a decrease in local temperature
○ Throughout each full cycle of day and night, one half of the Earth will be increasing in temperature and the other half will be decreasing in temperature
○ Overall, these local temperature changes balance out, and so the average temperature of the Earth remains roughly constant
How do lenses focus light
By refracting
Lenses can make images smaller or bigger. This is called …
Magnification
Lenses can be inverted (make them _)
Upside down
Lenses can make_or _images
Real
Virtual
What does real mean (in terms of lenses)
Can be projected onto a surface
What does virtual mean (in terms of lenses)
Cannot be projected onto a surface
What is white light made up of
Al the colours on the colour spectrum
_refracts the least and has the _ wavelength
Red
Longest
What is dispersion
When we can see the individual colours in the spectrum
Coloured objects only _ their own colour light
Reflect
Explain how ultrasonic waves are used to produce the image of an unborn baby
(partly) reflected when they hit a (boundary between two) different media
or substance or tissue
time taken for reflected wave (to return) is used to produce the image
Give a use for ultrasounds that isn’t to do with a baby
cleaning a delicate mechanism/jewellery welding plastics cutting textiles mixing emulsion paints sonar motion sensors (in burglar alarms) removing dental plaque industrial quality control breaking up kidney stones treating injuries
Ultrasound can be used in the industry for detecting internal cracks in metal. State two features of ultrasound
• humans cannot hear ultrasound
• it has a very high frequency / pitch
do not credit just ‘has a high frequency / pitch’
• above the (upper) limit for humans / above 20 000 Hz
