Topic 6 - Speed of waves + Reflection Flashcards
What is a transverse wave?
A wave where the oscillations are perpendicular to the direction of energy. (The vibrations go up and down)
What is a longitudinal wave?
A wave where the oscillations are parallel to the direction of energy, (The vibrations go left and right)
Give 2 examples for each wave type.
T - EM waves, waves in water, waves on a string.
L - Sound waves in air, shock waves.
What is the equation for working out the wave speed?
Wave speed = Frequency x Wavelength
What is the equation for working out the period of a wave?
Period (s) = 1/Frequency (Hz)
T = 1/F
How do you measure the speed of sound?
Attach a signal generator to a speaker to produce sound at a certain frequency.
Connect two microphones to an oscilloscope - making sure they show up as two separate waves.
Put them next to the speaker and move one further away until the waves match and record that distance.
Use the equation v=fλ to work out the speed using the wavelength you found and the frequency.
It should be around 330m/s
How do you measure the speed of water ripples?
Attach a dipper to the signal generator to create waves at a certain frequency.
Use a lamp to see the waves beneath the tank and measure the distance between 10 waves and divide by 10 to find one wavelength.
Use v=fλ to find the speed of the waves.
How do you measure the speed of waves in a solid?
Set up the signal generator to a vibration generator to create waves at a certain frequency. Then attach this to a string and hold it in place with a support at the opposite end.
Measure out 1 metre of the string and record the frequency at which you can see 1 wave in this distance.
Repeat this 5 times, increasing the frequency until the amount of waves increase by a half (make sure to still only measure the length of one wave)
Record the results and work out the speed.
What is the one rule for reflected waves?
Angle of incidence = Angle of reflection
What is specular reflection? Give and example.
When a wave is reflected in a single direction by a smooth surface. (E.G. when light hits a mirror)
What is diffuse reflection?
When a wave is reflected by a rough surface (like paper) and the rays are scattered in different directions.
How does diffuse reflection occur?
The normal is different for each ray so the angle of incidence is different.
