Topic 3.1 - General Wave Properties Flashcards
What is a wave?
A regular disturbance transferring energy in the direction of the wave’s propagation without transferring matter.
What is a transverse wave?
A wave in which oscillations are at right angles (perpendicular) to the direction of motion.
Give examples of transverse waves
Waves on a string, all electromagnetic waves (eg. visible light), ripples on water, vibrations on guitar strings
What is a longitudinal wave?
A wave where the oscillations are parallel to (in the same direction as) the direction of motion.
Give examples of longitudinal waves
Pulses along a spring, sound waves, ultrasound
Transverse waveforms have…
Peaks and troughs
Longitudinal waveforms have…
Compressions and rarefactions
Wavelength is…
The wavleegth of a wave is the distance between succesive crests
Frequency is…
The number of complete waves passing a given point per second, or the number of waves per second produced by the source.
State the wave equation
v =λ x f
- v = velocity (m/s)
- λ = wavelength (m)
- f = frequency (Hz)
What is refraction?
Refraction is the change in speed of a wave when crossing a boundary between two media, resulting in a change in direction.
Which property of a wave is not changed by refraction?
The frequency.
What happens when waves are incident on a flat surface?
Reflection
stronger reflected wave is produced when…
The surface is smoother
Why do rough surfaces appear matt when illuminated?
The reflected light rays are scattered in all directions.
When entering a denser material, light waves…
…slow down and bend towards the
normal.
When entering a less dense material, light waves…
…speed up and bend away from the normal.
What is diffraction?
The spreading out of waves passing through a narrow gap or across an edge.
What size of gap produces the largest diffraction?
A gap of the same width as the wavelength of the wave passing through it.
What is a ripple tank?
A shallow glass tank with an oscillating paddle/needle to create waves. It is illuminated from above so waves can be seen on the surface below the tank
Describe how to demonstrate reflection using a ripple tank.
Waves will reflect off the glass sides of the tank.
Describe how to demonstrate refraction using a ripple tank.
Place a glass box across half of the floor of the ripple tank. The waves will change speed when travelling through the less dense area.
Describe how to demonstrate diffraction using a ripple tank.
Place two glass blocks in the middle of the tank, leaving a small gap, and observe the wave patterns.
Transerve wave being sent along a rope
What is the amplitude of a wave
The amplitude is defined as the maximum displacement (movement away) from the rest or undisturbed level.
What are the three ways a wave’s direction of motion can change?
- Refraction
- Reflection
- Diffraction
How many ways can a wave change at a boundary?
3 times (refraction, reflection, diffraction)
Diffraction with different gaps
- If the gap size is very large relative to the size of the wavelength, the wave passes through with little diffraction.
- If the gap size is very small relative to the size of the wavelength, the amount of diffraction increases but not much of the wave will pass through the gap.
What causes a wave to diffract
- Corners
- Single edges
- Gaps
What happens when waves hit plane barriers?
- When a wave hits a smooth plane barrier, it is reflected so that its angle of incidence equals the angle of reflection
- When a wave hits a rough plane barrier, it is mostly refracted; the wave bends and travels through the plane barrier instead of reflecting
Interpret reflection and refraction using wave theory.
Angle of incidence = angle of reflection
