Waves and Optics Flashcards
Progressive wave def
A wave that transfers energy from one point to another without transferring the medium itself
displacement def
the distance of a point on the wave from its equilibrium position
It is a vector quantity; it can be positive or negative
amplitude def
the maximum displacement of a particle in the wave from its equilibrium position
wavelength def
the distance between points on successive oscillations of the wave that are in phase
(time) period def
time taken for one complete oscillation or cycle of the wave
frequency def and unit
the number of complete oscillations per unit time. Measured in Hertz (Hz) or s-1
What do the components of the wave speed equation mean
What does the wave speed equation show about frequency and wavelength
- As the wavelength increases, the frequency decreases
- As the wavelength decreases, the frequency increases
What is phase difference
how much a point or a wave is in front or behind another
How can waves phase difference be found
- from the relative positive of the crests or troughs of two different waves of the same frequency
- When the crests or troughs are aligned, the waves are in phase
- When the crest of one wave aligns with the trough of another, they are in antiphase
What is phase difference measured in
in fractions of a wavelength, degrees or radians
How many degrees/ radians correlate to in or out of phase
In phase is 360o or 2π radians
In anti-phase is 180o or π radians
traverse wave def
A wave in which the particles oscillate perpendicular to the direction of the wave travel (and energy transfer)
What kind of wave are electromagnetic waves
transverse waves
How can transverse waves be shown and can they be polarised
Transverse waves can be shown on a rope
Transverse waves can be polarised
Longitudinal wave def
A wave in which the particles oscillate parallel to the direction of the wave travel (and energy transfer)
Describe the compressions and rarefactions of longitudinal waves in terms of pressure
Compressions are regions of increased pressure
Rarefactions are regions of decreased pressure
How can longitudinal waves be shown and can they be polarised
Longitudinal waves can be shown on a slinky spring
Longitudinal waves cannot be polarised
Examples of transverse waves
Electromagnetic waves e.g. radio, visible light, UV
Vibrations on a guitar string
Waves on a string
Seismic (S) waves
Describe how energy is transferred through a longitudinal wave
- The particles in the medium vibrate as they are given energy
- The compressions cause the nearby particles to also vibrate with more energy
- This produces a compression further along in the medium
Examples of longitudinal waves
Sound waves
Ultrasound waves
Waves through a slinky coil
Seismic (P) waves
What is polarisation
Particle oscillations occur in only one of the directions perpendicular to the direction of wave propagation
Why can polarisation only occur in transverse waves
because transverse waves oscillate in any plane perpendicular to the propagation direction
What does it mean when transverse waves are polarised
Vibrations are restricted to one direction
These vibrations are still perpendicular to the direction of propagation / energy transfer