Yr 12 - Waves (1 of 2) Flashcards
What are mechanical waves? & what are they transferred through?
Waves that rely on particles to transfer energy.
- Energy is transferred through a medium.
What are EM Waves? & how are they transferred?
Waves that don’t rely on particles to transfer energy.
- Transfer energy through vibrations of electrical and magnetic fields.
What is a medium
The substance a wave is travelling through (air for example).
What do & don’t waves transfer?
Transfer energy without transferring matter.
What’s a progressive wave?
Transfer of energy due to oscillation of medium.
Examples of:
- Longitudinal waves
- Transverse waves
Longitudinal - Sound, P-waves
Transverse - Light, S-waves, all EM waves
Where is the equilibrium position?
Middle of wave (Horizontally) which the wave travels through.
What is meant by Frequency?
Number of waves passing a point per second.
What is meant by phase difference?
- Give examples on a graph for a wave.
Difference in phase angle of two waves.
- 0 phase difference between sections 2𝝅 apart (In Phase)
- Sections 𝝅 apart are out of phase by 𝝅
- Sections 1/2𝝅 apart are out of phase by 1/2𝝅
What is meant by ‘subtended through 2𝝅’?
The wave has travelled through 2𝝅
What Is the phase of a wave?
How far through a wave cycle a certain point has progressed.
- Eg, a wave that has travelled by 1/2𝝅 has phase of 1/2𝝅
What is wave speed?
Distance travelled by wave per unit time.
What is meant by ‘out of phase’?
Wave is neither in phase or anti phase.
What is ‘anti phase’?
Difference of exactly 𝝅 (180 degrees) between the phase of 2 waves.
Path Difference
Difference in distance covered by wave.
When ‘n’ is an integer and in terms of 𝝺. Describe these waves.
-> (n + 0.5)
-> (n)
-> (n+3.5)
-> (n+7)
-> (n+0.85)
- Anti phase
- Phase
- Antiphase
- Phase
- Out of phase
Do waves in phase have to have the same amplitude?
No but must cross medium at same point and have max displacement at the same time.
Why do longitudinal waves speed up in denser materials
Because of closer atomic structure energy can transfer faster.
How to light waves oscillate about the direction of energy transfer?
Perpendicular
What equation should you use when looking at graphs?
y = mx + c
Describe reflection
When a wave rebounds from hitting the boundary between 2 mediums.
Describe Refraction
Change in direction due to moving to a different medium.
Describe Diffraction
The spreading of waves around an obstacle/through a gap.
Describe polarisation
Reducing number of planes a wave travels in to one.
- Only applicable to transverse waves
Define intensity
Power transferred per unit area (usually by wave).
-> I = P/A (In EQ book)
How to Em waves travel?
Vibrate in both electric & magnetic field.
- Transverse
