P5 Flashcards
What is a wave?
Something that transfers energy without transferring matter.
Imaging particles vibrating to push the other but the returning to their original position
How do sound waves travel in the different states of matter?
Least in gas, highest in solids
This is because the particles are closer together
What is transverse wave?
A wave in which the vibrations are perpendicular to the direction of energy transfer.
Eg: light waves /EM waves
What is a longitudinal wave
Waves in which vibrations are parallel to the direction of energy transfer
Eg: sound waves
What should you imagine when looking at wave diagrams
That the wave is moving from left to right- even though draw as stationary
What is the normal line?
The mean position of a particle, about which it vibrates and oscillates
What is amplitude?
The maximum displacement of particles from their mean position.
Normal line to trough.
The more amplitude = more energy
What is the wavelength?
The distance from one peak to another peak
What is frequency?
The number of peaks passing a point every second.
Inversely proportional to wavelength
Eg large frequent, small wavelength
What are compressions?
Particles squashed together
High pressure
PEAKs
What are rarefactions?
Particles spread far apart
Low pressure
Troughs
What is the formula for wave speed?
Wave speed = frequency ✖️wavelength
C= f ✖️į (iambs)
Wave speed =m/s
Frequency =hertz (Hz)
Wavelength = m
What is the time period?
The time taken to produce 1 wave,
The equation is 1/ frequency = TP
1/TP= frequency
What is the only variable that can change the velocity of a wave?
The medium it is travelling , not the energy transferred
What does amplitude correspond to in sound?
The larger the amplitude, the larger the volume
What does frequency correspond to in sound?
The pitch,
The higher the frequency , the higher the pitch
What is the difference between longitudinal and transverse waves?
Transverse = oscillations are perpendicular
Longitudinal = oscillations are perpendicular
to the direction of energy transfer
Can an electro magnet travel in a vacuum?
Yes, does not require particles to travel
Describe electromagnet radiation:
A transverse wave that is a Light wave. Does not need particles to travel. The frequency/wavelength determines the colour of the light
How are electro magnetic waves created?
Vibrating charged particles
What is the difference between sound waves and EM waves?
Sound = vibrating particles
Transfer kinetic energy
EM= vibrating charged particles
Transfer electromagnet energy
List the EM spectrum in terms of increasing frequency:
〰️radio waves
〰️microwaves
〰️infrared waves
〰️visible light
〰️Ultra Violet waves
〰️X rays
〰️gamma ray
What must be noted about the frequency and wavelength of the EM spectrum ?
Increasing frequency = increasing energy
Increasing energy = smaller wavelength
How is the light intensity measured?
The amplitude of the EM radiation
What is the light intensity
The given light in a given time over a given area
What is the speed of light?
3 ✖️10^8
All EM waves travel at this speed
How are sound waves produced?
vibrating particles,
colliding with neighbouring particles,
transferring energy
Describe (visible) light waves
- Pass through air & glass but not other solids
- The see /cameras
Describe infra red waves:
1, pass through air, glass but are stopped by solids
2. night vision,toasters
3. Energy is absorbed by skin allowing it to heat up
Describe microwaves :
- Easily pass through the Earth’s atmosphere and air
- Used to cook food
- Heats up water particles
Describe Radio waves:
- Pass through air and solids
2.Radio and Tv signals
Describe Ultraviolet waves
- Can moderately penetrate Earth’s atmosphere but not skin
- Produces vitamin D
- A little ionising could possibly cause cancer
Describe X rays
- Penetrates skin and thin metal however is stopped by bone and dense metals
- Used for X-ray imaging
- Lightly ionising and can give rise to cancer
Describe Gamma rays
- Very penetrating !Stopped by thick lead materials
- Treatment of cancer
- Quiet ionising and can cause cancer
What two variables can you calculate from this graph?
What two variables can you calculate from this graph ?
how are electromagnetic waves produced?
vibrating charged particles,
oscillating electrostatic field,
moving magnetic filed
transfers electro magnetic energy
Can the frequency of a sound wave ever change.
No, only speed and wavelength
What is an ultrasound wave?
A wave that operated above 20,00Hz and so cannot be heard by humans , harmless to babies
transducers
What is a ‘boundary’?
the imaginary line between two different mediums
Definition of a transducer:
A device tear produces ultrasound waves by causing a crystal to vibrate rapidly
How are ultrasound scans produced?
- (Def) a transducer is a device that produces ultrasound waves by causing a crystal to vibrate rapidly.
- (Process) the transducer emits a pulse of ultrasounds
These waves are partially reflected every time they cross a boundary between different media.
The reflected ultrasound waves return to the transducer as a series o pulses which are deciphered to form an image.
Why are ultrasounds used to produce an image of mother’s womb?
Non -ionising (harmless to Fetus )
Reflected easily at boundaries, can clearly image soft tissue
Which medium do sound waves travel fastest in ?
Solid , because particles are closer together.
Why medium do light waves travel fastest in?
(Vaccum) otherwise gas
Why is cutting gel required?
Mimics fat.
Reducing the air gap between the transducer and skin, so that the ultrasound waves don’t immediately get reflected back
Describe the following oscilloscope trace
When do ultrasound waves reflect ?
When there is a change in density.
(Since ultrasound is a sound wave) it travels faster in denser mediums
The change is density changes the speed.
When there is change is speed , the wave reflects.
How
What is audible human range ?
20Hz - 20,000 Hz
(Eardrum can only vibrate this many times per second )
Label the parts of the ear
Label the parts of the ear
describe how the ear detects sounds
What is reflection?
When a wave reverses direction upon meeting the boundary between two media
What is the law of reflection?
The angle of incidence is equal to the angle of reflection, when the surface is smooth
Why use ultrasound instead of X rays
ultrasound waves are harmless sound waves which operate at a frequency above 20,000Hz (non -ionising)
X rays are a type of electromagnetic wave , with a high frequency that is ionising. This means that it could kill or damage some of the babies cells.
Ultrasound waves are easily reflected at boundaries, allowing some of the soft tissue and internal organs of the baby to be shown.
Draw a reflection diagram
What is a plane mirror ?
A mirror with a perfectly (flat or smooth surface)
All light is reflected
What is refraction?
When a wave changes direction, upon crossing the boundary between two media
In which media does light travel the fastest , and slowest
What is refraction ?
As a wave crosses the boundary between two media it’s speed and direction changes
(Observed to the eye to bend)
What happens in this scenario :
However is there is 0 angle of incidence (ray travelling along the Normal ) there won’t be any change in direction
Draw a reflection diagram
Draw how an image is formed in a mirror
What is the difference between an inverted and upright image ?
A inverted image is upside down
What is the difference between a virtual and real image?
A virtual image is basically imaginary, it is an image produced by a mirror that appears to be present , but cannot be seen on a screen.
However a real image is an image that you can put on a screen
rule of refraction
When a wave is travelling from a less dense to more dense medium?
The ray slows down and so moves towards the normal
rule of refraction
When a wave is travelling from a more dense to more less medium?
Speeding up , and so move towards the normal
Complete the diagram
What happens to the wave length of waves as they enter a more dense medium
what do lenses do ?
refract light
why are the shapes of concave and convex lenses ?
what do concave lenses do ?
What do convex lens do ?
describe short sightedness
Diverging rays which enter the ray are too converged
So are focussed before the retina
describe long sightedness
Cannot focus parallel rays from far away as lens is too weak to converge
Focused behind the retina
What is a real image
An image that is formed where the light rays meet.
The object is outside the focal length of a converging lens
What is a virtual image ?
An image that is formed where the light rays appear to come from.
The image formed inside the focal length for a converging lens.
When does an image appear magnified?
When an object is placed inside the focal Lemgo of a converging lens
Draw an object placed outside the principal focus for a convex lens
Draw an object placed inside the principle focus for a convex lens
Draw an object placed outside the principal focus for a concave lens
What is dispersion?
The separation of white light into it’s constditutent wavelengths .
This occurs because the different EM radiation have different frequencies and travel and different speeds , and so the angle of refraction differs. (The higher the frequency ,the higher the angle of refraction )
How do you perceive a colour ?
Eg this blue 🟦
The object is absorbing all other frequencies , but is then only reflecting that frequency (blue ). For this to be seen
What is specular reflection and diffuse scattering ?
Speculation reflection produces sharp images. Diffuse scattering produces no images. Beaches the rays do not come to focus
What are filters ?
Eg a blue filter 🟦
Will absorb all frequencies but will transmit others (blue )
*filters must be transparent
What colour light will be shown at the end ?
What do you calculate the “depth of boundary “?
Diverging
Separates the light rays, further away from each other
(concave lenses)
Converging
Bring the rays closer together
(convex lenses)
