Waves Flashcards
what 2 types of waves are there?
transverse
longitudinal
define transverse waves
oscillating perpendicular to the direction of energy transfer
define longitudinal waves
oscillating parallel to the direction of energy transfer
give an example of a transverse wave that isn’t a seismic wave
ripples on a water surface
what do longitudinal waves on a diagram show?
area of compression and rarefaction
how do you identify where there are areas of compression on a longitudinal waves diagram?
where the lines are closer to each other
how do you identify where there are areas of rarefaction on a longitudinal waves diagram?
where the lines are further apart
define amplitude
maximum displacement of a point on a wave away from its equilibrium
define wavelength
the distance from a point on one wave to the equivalent point on an adjacent wave
define frequency
the number of waves passing a point in each second
what is the formula to find period?
period = 1 / T
define wave speed
the speed at which energy is transferred through the medium
what is the formula to find wave speed?
Wave speed = frequency x wavelength
Describe a method to measure the speed of sound in the air
Measure distance travelled by wave using a meter ruler
Measure the time taken for the wave to travel the measured distance with a timer/stopwatch
Divide the distance by the time
what are the 3 things that can happen to a wave when it meets a boundary between 2 different materials?
reflection
refraction
absorption
What restricts the limits of human hearing?
Within the ear, sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound. The conversion of sound waves to vibrations of solid works over a limited frequency range
Describe processes which covert wave disturbances between sound waves and vibrations in solids
The human ear detects sound. Sound waves enter the ear canal and cause the eardrum to vibrate. Three small bones transmit these vibrations to the cochlea. This produces electrical signals which pass through the auditory nerve to the brain, where they are interpreted as sound.
What is the effects of sound waves on the ear drum?
Causes ear drum to vibrate
why do such process only work over a limited frequency range from and the relevance of this to human hearing:
Human hearing is limited by the size and shape of your ear drum, as well as the structure of all the parts within the ear that vibrate to transfer the energy from the sound waves
How are waves used for detection and exploration?
When a wave meets a boundary between two materials, it can be reflected or partially reflected.
The wave may continue travelling in the same direction, but at a different speed, or it could be absorbed or refracted
This can be used to study the paths of waves through structures and can give hints to some of the properties.
define ultrasound
a sound wave that is above the human range of hearing, 20kHz.
How are ultrasounds created?
- An ultrasound wave is transmitted and it will pass through the material
- The wave will meet a change in material density
- The wave will be partially reflected
- The detector records the time from transmission to detection and uses it to create an image based on distance
What are ultrasound waves used for?
- Pregnancy scan of the foetus - medical imaging
- Cleaning jewellery – industrial imaging
- Breaking kidney stones
what waves are produced by earthquakes?
seismic waves
give 2 features of p waves
longitudinal, travel at different speeds through solids and liquids
give 2 features of s waves
transverse, cannot travel through liquid
How do seismic waves provide evidence for the earths structure?
- When seismic waves reach a boundary between different layers of materials, some will be absorbed and some will be refracted
- If the waves are refracted then they will change speeds gradually
- By studying the path of these waves, we can see the structure of the earth
what is echo sounding?
High frequency sound waves can be used to detect objects in deep water and to measure water depth
how do lenses form images
by refracting light
define convex lens
brings light rays parallel to the axis to be brought together at the principle focus
define concave lens
causes parallel rays of light to be spread out (diverge)
define focal length
distance from lens to principle focus
what are ray diagrams used for?
used to show the formation of images by concave and convex lens
what lens will always produce a virtual image?
concave lens
what lens will either produce a virtual or real image?
convex lens
what are the similarities between concave and convex lenses?
Both converge parallel rays to a focal point, have positive focal lengths, and form images with similar characteristics
what are the differences between concave and convex lenses?
- A convex lens is thicker in the middle and thinner at the edges
- A concave lens is thinner in the middle and thicker at the edges
what is the formula to find magnification?
Magnification = image height / object height
what does each colour within the visible light spectrum have?
ts own narrow band of wavelength and frequency
what are the 2 types of reflection?
specular
diffuse
define specular reflection
reflection from a smooth surface in a singular direction
define diffuse reflection
reflection from rough surface causes scattering
how do colour filters work
by absorbing certain wavelengths and color and transmitting other wavelengths and color
what is the colour of an opaque object determined by?
which wavelengths of light are more strongly reflected
how does an object appear white?
if all the wavelengths are reflected equally
how does an object appear white?
if all the wavelengths are absorbed
what do opaque objects do, in terms of light?
do not transmit light, they absorb some wavelengths and reflect others
what do transparent and translucent objects do, in terms of light?
transmit light; all light is absorbed or reflected and some can pass through
what do colour filters filter out?
different wavelengths of light, so certain colors are transmitted and the rest are absorbed
what do colour filters filter out?
different wavelengths of light, so certain colors are transmitted and the rest are absorbed
what does a primary colour filter do, in terms of light rays?
only transmits the color; the rest will be absorbed
what does a colour filter do, in terms of light rays?
let though both wavelengths of for that color to reduce the effect of random errorscolor they are made up of
A red filter is placed in front of the spotlight.
The spotlight is directed at a blue object
Explain why the blue object appears black.
only red is transmitted by the filter
red is absorbed by the (blue) object
(so) no light is reflected by the (blue) object
What is the advantage of repeating measurements and calculating a mean?
to reduce the effect of random errors
What is the advantage of repeating measurements and calculating a mean?
The ray of light from the ray box should be as narrow as possible.
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 (in the measurements)
Give two ways in which radio waves are different to sound waves
* (radio waves are) transverse
allow sound waves are longitudinal
allow a description of transverse/longitudinal waves
* (radio waves) travel at a higher speed
* (radio waves) don’t need a medium
allow (only) radio waves travel through a vacuum
* (radio waves are) electromagnetic
allow sound waves are mechanical
which electromagnetic wave has the highest frequency?
gamma rays
