P1-Waves Flashcards
Describe and give an example of a longitudinal wave.
Longitudinal waves vibrate parallel to the direction of energy transfer.
A longitudinal wave is made up of compressions and rarefactions.
Sound waves and P waves are longitudinal.
What type of wave is a mechanical wave?
Mechanical waves can be both transverse or longitudinal.
Mechanical waves travel through a medium.
Define amplitude.
The amplitude of a wave is the maximum disturbance from its rest position.
Define wavelength.
The wavelength of a wave is the distance between a point on one wave, and the same point on the next wave.
Define frequency.
The frequency of a wave is the number of waves per second and is measured in hertz (Hz).
How do you calculate wave speed?
Give the units.
The speed of a wave can be calculated by:
Frequency (Hz) x Wavelength (m) = Wavespeed (m/s).
Define reflection.
The mirroring of light, heat or sound without absorbing it.
Define refraction.
The changing direction of waves according to material density.
Define diffraction.
The spreading out of waves when they pass through a gap or around an obstacle.
What is the normal?
The normal is a line drawn perpendicular to the surface.
What difference between a virtual image and a real image?
A real image can be formed on a screen because the rays of light that produce the image can pass through it.
A virtual image cannot be formed on a screen because the rays of light that produce the image only appear to pass through it.
How does a change in medium and speed cause waves to change direction?
As light waves enter a denser substance they slow down and the wave changes direction towards the normal.
As light waves enter a less dense medium they speed up and the wave changes direction away from the normal.
What is the law of reflection?
The law of reflection states that the angle of incidence is equal to the angle of reflection.
How does the gap size affect diffraction?
The narrower the gap the greater the diffraction.
The wavelength needs to be similar to the size of the obstacle or gap in order to diffract.
Why can hilly areas receive radio signals but not terrestrial TV signals?
TV signals have short wavelengths and so do not diffract around the hills whilst the radio waves have longer wavelengths which can diffract around the hills because they are a similar size to the hill.
What is the frequency range of the normal human ear?
From about 20Hz to 20kHz.
