P12 and P13 Revision Flashcards
To revise Chapter 12 and 13 (51 cards)
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.
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.
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.
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
Define frequency
It is the number of waves that pass a point per second. Measured in hertz (Hz)
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
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
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.
What is refraction?
When a wave travels from one medium to another and changes direction.
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
When light speeds up which direction does it refract?
Away from the normal
Explain why light refracts as it passes from air into glass?
As light moves from air into glass it slows down.
The edge of the wave front entering the glass first slows down first
Part of the wave front that is still in the air continues at a higher speed causing it to travel further and to change in direction
State the normal human hearing range
From 20 Hz to 20 kHz
How do we detect sound waves?
Within the ear, sound waves cause the ear drum and other parts to vibrate. These vibrations are converting into an electrical signal which is passed onto the brain.
