Displacement, Phase Difference, Coherence and Path Difference Flashcards
Define Displacement.
This is the distance and direction that the particle is from the equilibrium position.
Define Phase Difference.
The description of when a given point on one wave lags behind the exact same point on another wave.
It is NOT expressed as a distance – it is expressed as an angle in either degrees or radians.
(1 whole cycle is 360° = 2π radians)
What is the equivalent of completing one wave length?
It is the equivalent to an object moving in a circular path and completing 360º (or 2π).
What is the angle of a ¼ λ (Wave length)?
State the angle in radians.
What does ¼ of a wave length (λ) mean?
Angle = 90º
Number of wavelength = 1/4 of a λ (Wave length)
Angle in Radians = π /2
What does ½ λ (wavelength) represent?
What is the angle of a ½ a wavelength?
State the angle in radians.
1/2 a λ = Number of Wavelength.
Angle = 180º
Angle in radians = π
What does ¾ of a wavelength (λ) represent?
What is the angle of ¾ of a wavelength?
State the angle in radians.
¾ of a wavelength (λ) = Number of Wavelength.
Angle = 270º
Angle in radians = 3/2 π
What does a wavelength (λ) represent?
What is the angle of a wavelength (λ)?
State the angle is radians.
λ = Number of Wavelength
Angle = 360º
Angle in Radians = 2π
What does coherent light consist of?
They consists of waves with the same frequency, amplitude and phase.
Give an example of a non-coherent wave and what do they produce?
Light from a torch or Sunlight contains waves with different wavelengths, producing different colours all mixed together.
Give an example of a coherent wave and state the term used to describe that the waves have the same frequency and wavelength.
Laser light is an example of a coherent wave.
The term is ‘monochromic’ to describe that all the waves have the same frequency and wavelength.
State why Monochromic light can also be coherent?
This is because they are needed to produce the stable interference patterns.
Give an example of a coherent wave source.
What does it produce?
What does this mean?
Lasers are an example of a coherent wave source.
It produces light that is monochromatic.
This means that each wave has one frequency or wavelength. Each wave also has the same amplitude, and they are in phase with one another.
Define Path Difference.
The difference (in meters) between the lengths of two paths.
Describe the features of two waves when they reach the same phase difference.
When two waves have the same frequency, and travel at the same velocity, and travel the same distance they will keep the same phase difference.
Describe what happens if one of the waves have to travel a longer path.
if one of the waves has to travel a longer path it will be out of phase by the time it gets to the same point as a wave travelling the more direct path.
