waves Flashcards
Name the two types of waves
- Transverse
- Longitudinal
Define transverse waves
- The direction of oscillation is perpendicular to the direction of energy transfer
Name examples of transverse waves
- Electromagnetic waves like light and microwaves, ripples on a water surface
Define longitudinal waves
- The direction of oscillation is parallel to the direction of energy transfer
Name examples of longitudinal waves
- Sound waves travelling through air
What is the difference between transverse and longitudinal waves (medium)
- All longitudinal waves require a medium to travel through (gas, liquid, solid) whereas some transverse waves can travel through a vacuum e.g., electromagnetic waves
What is the purpose of all waves?
- They transfer energy from one place to another
e.g., ripples transfer kinetic energy, sound waves transfer sound energy
Describe evidence that for ripples on a water surface, it is the wave and not the water itself that travels
- If you place a floating duck on a water wave (transverse) the duck will bob up and down but will not move from side to side
Describe the evidence that for sound waves in air, it is the wave and not the air itself that travels
- If you use a slinky to model a longitudinal wave and mark a fixed point on the slinky, it will move side to side but does not travel through the medium
What is the top of the wave called?
- The peak or the crest
What is the bottom of the wave called?
- The trough
Define the amplitude of a wave
- The maximum displacement of a point on a wave away from its undisturbed position
Define the wavelength of a wave
- The distance from a point on one wave to the equivalent point on the adjacent wave
Define the frequency of a wave
- The number of waves passing a point each second
Define the wave speed of a wave
- The speed at which the energy is transferred (or the wave moves) through the medium
Define the period of a wave
- The time taken for one wave to pass a point
How can you measure the speed of sound waves in the air?
1) Person A has cymbals, person B has timer
2) Make them stand 500m apart
3) Person A crashes cymbals together; person B starts stopwatch when they see person A crash cymbals and stops stopwatch when they hear crash of cymbals
4) Calculate speed of sound waves by doing S=D/t
How can you use an oscilloscope to measure speed of sound?
- Set up the scope sot he detected waves at each microphone are shown as separate waves
- Start with both microphones next to the speaker, then slowly move one away until the two waves are aligned on the display but have moved exactly one wavelength apart
- Measure distance between phones to find one wavelength
- Use formula for wave speed
What are the problems with the experiment for measuring speed of sound waves in air? How to resolve them?
- Different people have different reaction times, giving way for inaccuracies
to overcome this - We can use a large number of observers with timers and calculating a mean
- It is only a very short space of time between seeing cymbals crash and hearing them, making it very difficult to press stopwatch at correct times
- Increasing distance between the people can reduce this problem
What happens to waves between two different materials (at the boundary)?
- At the boundary, they can be reflected, absorbed or transmitted
What happens when a wave is absorbed?
- Transfers energy to the material’s energy stores
What happens when a wave is transmitted?
- Waves carry on travelling through the new material
- Often leads to refraction
What does the activity of a wavelength depend on (absorb transmit reflect)?
- Properties of the materials involed
Describe how you would draw a simple ray diagram for reflection
- Angle of incidence = angle of reflection
- Draw incoming ray, hitting the boundary and normal line (perpendicular
- Draw reflected ray at the same angle
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