P6 Waves Flashcards
How can an image appear on a ray diagram? (6)
- virtual
- real
- upright
- inverted
- enlarged/magnified
- diminished
Explain why a blue object appears black through a red filter
The filter only transmits red waves. The blue object only reflects blue waves so red is absorbed by the object and so no light is reflected by the object.
Give three uses of UV
- skin tanning
- sterilising equipment
Describe the difference between transverse and longitudinal waves
in a transverse wave, the oscillations are perpendicular to the direction of energy transfer whereas in a longitudinal wave, the oscillations are parallel to the direction of energy transfer
What is the advantage of repeating measurements and calculating a mean?
Reduce effect of random errors, giving a more accurate reliable mean
Explain how the teacher could determine the speed of the wave if they didn’t measure the wavelength of the wave
- Measure the distance travelled by a wave using a metre rule
- Measure the time taken (for the wave to travel the measured distance) with a timer
- Divide the distance by the time to give speed
Explain why using a wider ray would give less accurate results than using a narrower ray.
it is harder to judge where the centre of a wider ray is causing a larger uncertainty and so less accuracy
Explain how to get data on the angle of incidence and refraction from given angles (RPA)
- place a glass block on a piece of paper and draw around the glass block then remove the block
- draw a line at 90° (the normal) to one side of sketch
- use a protractor to measure and then draw a line of a given angle of incidenc to the normal
- place block back on the trace then use the ray box to shine a ray of light through the glass block at a measured angle
- mark the incident ray (entering the glass block) and the refracted ray of light emerging from the glass block
- remove the block and draw path of refracted ray through the block, then measure the angle of refraction with a protractor from the normal
- repeat the procedure for a range of values of the angle of incidence
Describe what happens in the electrical circuit when an aerial absorbs radio waves
Alternating current is induced (electrons oscillate) with the same frequency as the radio wave
Describe two differences between radio waves and sound waves
- radio waves are transverse, sound are longitudinal
- radio waves don’t need a medium as they can travel through a vacuum
Explain why the study of seismic waves provides evidence for the structure of the Earth’s core
S-waves cannot travel through a liquid and so S-waves do not travel through the (outer) core - can understand internal structures better
What makes microwaves suitable for sending communications to a satellite in space?
Can travel through the atmosphere (not reflected by ionosphere)
What is a perfect black body?
The object is the best possible emitter of radiation: absorbs and emitts all radiation and doesn’t reflect or transmit any
What is the function of a microphone?
To convert sound (waves) into variations in current / p.d
Explain how the properties of X-rays make them suitable for the medical imaging of bones.
Can pass through soft tissue but be absorbed by bone (high frequency and short wavelengths)
How can the hazard of boiling water be dealt with?
Use slightly cooler water
Explain why scientists replace an old scientific model with a new model.
Include an example from Physics in your answer
- New evidence may mean old models are incorrect
- The new model will explain new evidence
- Ie plum pudding model replaced by nuclear model
Explain why waves diagonally changing from deep to shallow water refract
Velocity is slower in shallow water so as edge of wave (front) entering shallow water at an angle slows down, part of the wave (front) in deeper water continues at a higher speed (leading to a change in direction of the wave fronts due to different velocities)
Explain why waves travelling parallel from deep to shallow water do not refract
Every point on the wave (front) enters the shallow water at the same time so every point slows down at the same time
RPA 9: what is a possible random error?
Not putting ray box in the same position each time
State one change of apparatus to investigate diffuse reflection.
Using a rough irregular reflecting surface
What is an ultrasound?
Sound waves with a frequency above the upper limit of human hearing range (above 20kHz)
State three uses of ultrasound
- Pre natal scanning/imaging
- Destroying kidney stones
- Cleaning jewellery
State one advantage and disadvantage of X Rays
A: can image any part of the body
D: ionising radiation so increased risk of mutations and so can become cancerous
Explain one possible inaccuracy when trying to measure the angle of incidence and refraction
The width of the light ray
which makes it difficult to judge where the centre of the ray is
Explain reason why light is refracted as it crosses from air into glass
Light waves enter a more dense material so velocity decreases (light waves bend towards the normal)
Describe how the wavelength of the water waves in a ripple tank can be measured accurately.
Use a (metre) ruler to measure 10 waves and then divide by 10
If the amplitude has become smaller what has the sound become?
Quieter
Explain why there is no sound in space
Sound cannot travel through a vacuum as needs particles to vibrate to make sound, as space is a vacuum there are no particles to vibrate and make sound
What does the frequency of a sound wave determine (more waves are seen)?
Pitch
What does amplitude of a sound wave determine?
Loudness
What does amplitude of a light wave determine?
Brightness/ intensity of colour
What does the frequency of a light wave determine?
Energy (high frequency = carry more energy)
Do you think the ultrasound experiments on mice were justified?
Explain your answer
Unethical to experiment on humans so it is better to experiment on mice
Explain what scientists should do if they find evidence that ultrasound may be harmful to human health.
Carry out more research to check reliability of findings
Describe the features of ultrasound and what happens after it has entered the body
- longitudinal waves
- frequency above 20kHz (upper limit of human hearing)
- Ultrasound is partially reflected when it meets a boundary between two different media
Describe the features of X-rays and what happens after it has entered the body
- EM transverse waves with a short wavelength and high frequency
- Ionising radiation
- Absorbed by bone and transmitted through skin (soft tissue)
What is a virtual image?
image cannot be formed on a screen, light doesn’t actually pass through it
Compare radio waves and sound waves (4)
- radio waves are transverse, whereas sound waves are longitudinal
- radio waves can travel through a vacuum, sound waves can’t
- radio waves travel at the speed of light
- radio waves have higher frequencies
What are the primary colours of the visible light spectrum?
Red green and blue
How can seismic waves be detected?
Using seismometers
Explain what happens when sound waves travel from a less dense medium, to a more dense medium
Their speed increases, as sound requires particles to vibrate to move, there are more particles closer together in denser materials so vibrations can travel quicker and easier (by collisions)
What is the problem with using an oscilloscope to measure sound waves?
Represents sound waves as transverse waves, although they are longitudinal
What is a reflected sound wave called?
An echo
What happens to wavelength and frequency if wave speed increases?
Wavelength increases
Frequency stays the same
Explain why drawing a protractor on paper is better than using a normal protractor
Angle of incidence and reflection will be more easily read and won’t be confused
What are the three primary colours
red, blue and green
Define wavespeed
Speed energy is transferred through a medium (per second)
Define amplitude
Maximum displacement of a point on a wave from its undisturbed position
Define refraction
Change of direction of a wave at a boundary between two different materials
