CP4 Flashcards
What are waves?
A way of transferring energy or information without transferring matter. Many waves travel when particles pass on vibrations.
What are the two types of waves?
- Transverse waves
- Longitudinal waves
What are transverse waves?
A wave where the vibrations are at right angles to the direction in which the wave is travelling.
What are longitudinal waves?
A wave where the vibrations are parallel to the direction in which the wave is travelling (this can be shown with a slinky moving parallel)
What is Wave Frequency?
The number of waves passing a point each second.
What are some examples of transverse waves?
- Light waves
- Ultraviolet radiation
- Water waves
- S waves (Earthquakes)
What are some examples of longitudinal waves?
- Sound waves
- Ultrasound waves
- P waves (Earthquake)
What is Wave Frequency measured in?
Hertz (Hz).
What is a period on a wave?
The length of time it takes one wave to pass a given point.
Where is wavelength measured from in a longitudinal wave?
It is measured from one compression to another compression.
What is the symbol for wave length?
Lambda (λ)
What is the wavelength of a wave?
It is the distance from a point on one wave to a point in the same position on the next wave. It is measured in metres (m).
What is the amplitude of a wave?
The maximum distance of a point on the wave way from its rest position (it is measured from the middle line of the wave to the top most point on a wave), the greater the amplitude of a sound wave, the louder the sound.
What is the trough on a wave?
It is the bottom most point of a wave.
What is the crest on a wave?
It is the top most point of a wave.
What is the equation for wave speed (involving distance and time)?
Wave speed(m/s)=distance(m)/time(s)
What is the equation for wave speed (involving frequency and wave length)?
Wave speed(m/s)=frequency(Hz) x Wavelength(m)
What does the speed of a wave always depend on?
It always depends on the medium that the wave is travelling through. Light travels slower in glass and water than in a vaccum.
What are the units for the equation for wave speed (involving frequency and wavelength)?
v= f x λ (v=speed, f=wave frequency, λ=wavelength)
What is the formula triangle for the equation for wave speed (involving frequency and wave length)?
Wave speed
Frequency | Wavelength
What is the speed of light in a vacuum?
300,000,000m/s
What happens to the wavelength of light when going from air to water?
The wavelength reduces.
How can you measure the speed of sound?
By measuring the time it takes for a sound to travel in a certain distance (e.g. standing in front of a large wall and measuring how long it takes for the echo sound to reach you), then because you have the time taken and the distance between you and the wall, you can use the distance time equation to work out the speed.
How can you measure the speed of waves in water?
By measuring the time it takes for a wave to travel between two fixed points such as buoys. The speed can be calculated from the time and distance between the points.
What is refraction?
The change in direction when a wave goes from one transparent material to another.
What direction does light refract when going from air to glass/water?
Towards the normal.
What direction does light refract when going from glass/water to air?
Away from the normal.
What is the normal line in refraction?
An imaginary line drawn at right angles to the surface of a mirror or lens where a ray of light hits it.
What direction does light travelling along the normal line go towards when going into a different medium?
Light travelling along the normal line does not change direction when going into a different medium.
Why do objects seem closer than they really are in water?
As light reflected by it changes direction when it leaves the water.
Does light travel faster in air or glass/water?
Light travels faster in air.
What happens to the speed of the light as it changes between one medium and another?
As light passes from one medium to another, it changes speed which causes the direction of the light to change.
What does the bend of the refraction depend on?
It depends on how fast the light travels in the two media and the angle of the light hitting the interface. The greater the difference in speed between the two media, the more the light is bent.
When does light bend towards the normal?
When light slows down.
When does light bend away from the normal?
When light speeds up.
How does the depth of water affect the speed of waves in water?
Waves moving from deep water into shallow water slow down and change direction to move towards the normal. Waves moving from shallow to deep water speed up and change direction to move away from the normal.
