Chapter 12 - Waves and vibrations Flashcards
What are transverse waves?
Vibrations that are perpendicular to the flow of energy.
What is a progressive wave?
A wave which energy moves in one direction.
How can you distinguish between longitudinal and transverse waves?
Transverse waves can be polarised but longitudinal can’t.
What does polarisation mean?
To allow waves to vibrate in only one plane. Unpolarised waves change from one plane to another.
Where would you find polarising filters?
Sunglasses to reduce glare.
3D cinema spectacles to see 3D movies.
Windscreens to reduce glare.
Define the amplitude of a wave.
The maximum displacement of a particle from its equilibrium position.
Define wavelength.
The maximum distance between two adjacent crests or particles with the same displacement and velocity.
Define frequency.
Number of cycles of a wave in one second.
What is superposition?
When two waves meet, the total displacement is the sum of the individual,displacements at that point.
How is a stationary wave set up?
Waves with the same frequency and wavelength travelling in opposite directions form nodes (areas of no displacement) and antinodes (areas of maximum displacement). Nodes are the result of destructive interference and antinodes the result of constructive interference.
What are coherent waves?
Waves with the same frequency and a constant phase difference. These are waves that form interference patterns when they overlap.
What is monochromatic light?
Light containing only one wavelength.
What is the difference between a progressive wave and a stationary wave?
There is no net transfer of energy in a stationary wave.
What is a longitudinal wave?
The direction of vibrations is parallel to the flow of energy, composed of areas of compressions and rarefactions.
Describe the vertical displacement of a particle in a transverse wave from the start of the cycle.
Moves vertically upwards to max displacement for a 1/4 cycle, then vertically downwards to equilibrium position, then vertically downwards to maximum negative displacement then finally vertically upwards for the last 1/4 cycle to equilibrium position.
How would a particle in a wave become motionless?
A wave with the same frequency and amplitude moving in the opposite direction destructively interferes to form a node. A stationary wave forms. Waves cancel where the particle is. Node = no movement.
What is an antinode?
Point of maximum disturbance on a stationary wave. This is caused by constructive interference of in phase waves.
What is a node?
Two waves cancel due to 180degrees phase difference.
A point of minimum or no disturbance.
Explain why it is important to correctly align an aerial of a TV in order to receive the strongest signal.
Radio waves are often polarised. Aerials must be aligned in the same plane of the wave.
If a seismic wave is polarised what does it tell you about the wave?
It is a transverse wave as longitudinal waves can’t be polarised. The oscillations of this wave are in one plane.
Seismic waves can be transverse or longitudinal.
How can a player of a stringed instrument increase the fundamental frequency of a note?
Decrease the length of the string
Increase the tension of the string
Tighten the string
Give an example of a transverse and longitudinal wave.
Anything on the electromagnetic spectrum, water waves, wave on a rope.
Sound wave
Seismic waves can be both.
How does the wavelength of a stationary wave change as the frequency is tripled?
Wavelength decreases by a factor of 3 as frequency is inversely proportional to wavelength.
What’s the difference between phase difference of two waves and the path difference?
Phase difference is given in degrees.
Path difference is given in fractions of a wavelength.
