4. Waves Flashcards
What do waves transfer?
Waves transfer energy and information.
What do waves not transfer?
Waves do not transfer matter.
What are the two types of wave?
- Transverse
- Longitudinal
What is a transverse wave?
A wave for which the oscillations are perpendicular to the direction of energy transfer.
What is a longitudinal wave?
A wave for which the oscillations are parallel to the direction of energy transfer.
Give three examples of transverse waves.
- Electromagnetic waves
- Seismic S-waves
- Ripples in water
Give two examples of longitudinal waves.
- Sound waves
- Seismic P-waves
What are the two parts of a longitudinal wave called?
Compressions and rarefactions.
What are the two parts of a transverse wave called?
Peaks and troughs.
What is a wave’s amplitude?
The maximum displacement of a point on a wave from its undisturbed position.
What is wavelength?
- The distance from a point on a wave to the same position on the adjacent wave.
- Most commonly peak to peak or trough to trough.
What is the frequency of a wave?
The number of waves that pass a given point each second.
What is the unit used for frequency?
Hertz, Hz
What is meant by a frequency of 200Hz?
200 waves pass a given point each second.
What is wave speed?
The speed at which energy is transferred through a medium.
What is wave velocity?
Wave velocity (measured in metres per second) is equal to the product of the wavelength and frequency of the wave.
What is meant by the period of the wave?
The length of time it takes for one full wave to pass through a point.
period = 1 / frequency
What word is used to describe when a wave bounces off a surface?
Reflection
What is the normal (in terms of reflection and refraction)?
A vertical imaginary line which is perpendicular to the boundary.
What occurs when light is reflected off a boundary?
It bounces off a smooth flat surface so that the angle of incidence (the angle it comes in at) is the same as the angle of reflection (the angle it leaves at).
What is refraction?
Refraction is the change in speed of a wave as it reaches a boundary between two materials at an angle to the normal, usually resulting in a change in direction.
What occurs when light is refracted at a boundary?
- The light changes speed and direction in the new medium.
- If the new medium is more dense, the light will travel slower and bend towards the normal.
- If the new medium is less dense, the light will travel faster and bend away from the normal.
When entering a denser material, light waves …
… slow down and bend towards the normal.
When entering a less dense material, light waves …
… speed up and bend away from the normal.
How can refraction be measured?
The angle of incidence, i, and angle of refraction, r, can be measured and compared. All angles are measured relative to the normal.
What are the effects of absorption of different wavelengths of waves in different mediums?
- Some materials behave differently depending on the wavelength.
- An example is glass which will transmit visible light, but reflect UV light.
How do sound waves travel through a solid?
The particles in the solid vibrate and transfer kinetic energy through the material.
Does frequency change during refraction?
Frequency never changes during refraction.
