4.4 Waves 1 Flashcards
What is a progressive wave?
A progressive wave is an oscillation that travels through matter. In some cases they can travel through a vacuum. They transfer energy, not matter.
Why is sound a progressive wave?
Sound vibrations travel to your ears but the air particles do not.
What is a transverse wave?
A wave in which the oscillations or vibrations are perpendicular to the direction of energy transfer.
What is an example of a transverse wave?
Water waves, electromagnetic waves, s-waves produces in earthquakes.
What is a longitudinal wave?
A wave in which the oscillations or vibrations are parallel to the direction of energy transfer.
What is an example of a longitudinal wave?
Sound waves, p-waves produced in earthquakes.
What does compression mean?
A moving region in which the medium is denser/has higher pressure than the surrounding medium.
What does rarefaction mean?
A moving region in which the medium is less dense/has lower pressure than the surrounding medium.
What is the definition of the time period of an oscillation?
The number of wavelengths passing a point per unit time.
Time Period = 1/Frequency (Hz)
How are time period and frequency related?
They are reciprocals of each other.
What is the wave equation?
Wave speed (ms-1) = Frequency (Hz) x Wavelength (m)
What is a wave profile?
A graph showing the displacement of particles in the wave against the distance along the wave.
What is phase difference?
Phase difference describes the difference between the displacement of particles along a wave, or difference between displacements of particles of different waves.
What are the units of phase difference?
Degrees or radians.
What does it mean if two particles are in phase?
If particles are oscillating perfectly in step with each other and both reach maximum positive displacement at the same time, they are in phase.
What does it mean if two particles are in anti phase?
If a particle reaches maximum positive displacement as another reaches maximum negative displacement, they are oscillating completely out of step with each other, and are in anti phase.
How can phase difference be calculated for two points separated by distance x on a wave?
Phase Difference (degrees/radians) = Distance (m)/Wavelength (m)
What piece of equipment can be used to determine the frequency of a wave?
An oscilloscope.
What is the reflection of a wave?
The change in direction of a wave at a boundary between two different media, so the wave remains i the original medium.
What does the ray show on a ray diagram?
The direction of energy transfer and so the path taken by the wave.
State the law of reflection.
The angle of incidence is equal to the angle of reflection.
When a wave is reflected, do wavelength or frequency change?
They stay the same.
What is refraction?
The change in direction of a wave as it passes from one medium to another.
What happens if a wave slows down upon entering a different medium?
It will refract towards the normal.