P5 Waves in Matter Flashcards
Refraction
When a wave travels from one medium to another and its velocity and direction change
Reflection
Waves reverse direction
Diffraction
Waves spread out
Wave phenomena can only occur at…
The boundary between two media
Wave phenomena can only occur when…
A wave changes speed
The angle of incidence is equal to the angle of reflection
i=r
What is ultrasound
The name given to sound waves with a frequency greater than 20,000Hz
What is a wave?
Am oscillation that transfers energy
Mechanical waves
Need a medium to travel through
e.g. sound and water
Longitudinal
Direction of vibrations is parallel to direction of the wave
e.g. sound waves
Transverse
Direction of the vibrations is perpendicular to the direction of the waves
Frequency
Number of waves, or oscillations, per second
Time period
Time taken for a wave to pass a point
Wavelength
Distance from one point on the wave to the same point on the next
Amplitude
Distance from the middle of the wave to the top (crest) or the bottom (trough) of the wave
Wave Velocity (m/s)=
Frequency (Hz) x Wavelength (m)
Vibrations of a transverse wave are perpendicular to the waves direction of travel. List some transverse waves.
EM waves
S-waves
Water waves
List some longitudinal waves
Sound waves
P-wave
How could you generate water waves at a fixed frequency in a ripple tank?
Use a dipper attached to a signal generator. The signal generator moves the dipper up and down at a constant frequency, which creates waves with the same frequency.
How could you find the frequency of a water wave in a ripple tank using a cork and a stopwatch?
Float the cork on the water. Start the stopwatch when the cork is at the top of a ‘bob’ and count how many times the cork bobs with the waves in a set amount of time. Divide the number of bobs by the time interval (in seconds) to find the frequency.
Why does milk appear white?
Because the particles scatter all wavelengths.
Why does ink appear black?
Because the particles absorb all wavelengths.
