P12 and P13 Revision Flashcards
To revise Chapter 12 and 13
What do waves transfer?
Energy
What are the two types of wave?
Transverse and longitudinal
Describe a transverse wave
The vibrations of the wave are perpendicular** to the direction in which **energy is transferred.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/677/a_image_thumb.jpeg?1587714363)
Give some examples of transverse waves
Ripples on a water surface
Any wave in the electromagnetic spectrum
S waves
Describe a longitudinal wave
The vibrations of the wave are parallel** to the direction in which **energy is transferred.
Longitudinal waves show areas of compression** and **rarefaction.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/682/a_image_thumb.jpeg?1587714415)
Give some examples of longitudinal waves
Sound waves
Ultrasound
P waves
Define amplitude
The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed (equilibrium) position.
It shows us how much energy a wave has.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/686/a_image_thumb.png?1587714496)
Define wavelength
The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave. Measured in meters
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/689/a_image_thumb.png?1587714531)
Define frequency
It is the number of waves that pass a point per second. Measured in hertz (Hz)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/692/a_image_thumb.png?1587714553)
Define period (T)
Its the time for one exact wave to pass a point. Measured in seconds
T = 1 / f
State the wave equation with all units
wave speed (m/s) = frequency (Hz)× wavelength (m)
Describe an experiment to find the speed of sound through air
- Measure a distance of 100 m from a wall.
- Hit two blocks together to make a sound and start timing.
- Stop timing when the hear the reflected sound (echo).
- Divide the time recored by 2 as the sound has travelled to the wall and back again
- use the equation Speed = distance / time
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/700/a_image_thumb.png?1587714710)
Describe a method to measure the speed of ripples on a water surface.
- Set up a ripple tank.
- Find the wavelength by using a ruler to measure across 10 wavelengths.
- Divide the answer by 10 to find 1 wavelength.
- Use a stopwatch and count the number of waves produced in 10 seconds.
- Dived the answer by 10 to find the frequency.
- Use the equation speed = wavelength x frequency
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/705/a_image_thumb.jpeg?1587714736)
What can happen to waves when they reach a boundary between two materials?
- They can be reflected
- They can be absorbed (this will cause a small temperature rise)
- They can be transmitted (they will pass through)
What is the law of reflection
The angle of incident = angle of reflection for a flat plain mirror.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/709/a_image_thumb.jpeg?1587714787)
What is refraction?
When a wave travels from one medium to another and changes direction.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/464/754/711/a_image_thumb.jpeg?1587714807)
Why does refraction take place?
The change in medium means a change in density which caused a change in speed.
When a substance moves from a more dense to a less dense substance, what is the affect of waves speeds, frequency and wavelength?
- Wave speed - decreases
- Frequency - same
- Wavelength - decreases
When a substance moves from a less dense to a more dense substance, what is the affect of waves speeds, frequency and wavelength?
- Wave speed - increases
- Frequency - same
- Wavelength - increases
When light slows down which direction does it refract?
Towards the normal