OP - Diffraction, Wave Optics, and Coherence - Week 4 Flashcards
Describe Newtons model for reflection.
Corpuscles of light bounce off the boundary, with their vertical velocity reversed, and their horizontal velocity unchanged.
Describe Newton’s model for refraction.
He argued corpuscles travelled faster in glass so their vertical velocity was accelerated by an attractive force exerted by the medium it travelled in.
What is an argument in favour of light being composed of waves, and not particles?
Light rays can cross each other without hindrance, which would be difficult for particles.
What are Newtons rings?
Interference patterns
Describe diffraction.
The bending of a wavefront as it passes through a narrow aperture or across an edge. Only wavefronts close to the edge are diffracred.
Describe interference.
Waves can summate to form constructive interference where their amplitudes are summed, or they can be destructive where their maximum and minimum amplitudes cancel each other out when summed.
Define coherence, including spatial and temporal coherence.
It is the degree to which the local phase of a wave can be predicted by watching nearby waves at the same time (spatial coherence), by observing what has happened locally in the immediate past (temoral coherence).
Describe the principle behind why interference patterns occur despite single quanta being fired at the two slits at a time.
Heisenburg’s uncertainty principle - position and velocity may not be known at the same time, due to inherent uncertainty, applying to time and energy.
Observing which slit the discrete quanta go through will collapse the interference pattern, and result in solid slits, and this is due to the observer effect.
What happens with circular apertures and diffraction? What is the implication of this?
Circular apertures result in a fringed image, concentric circles around a central disk, kown as Airy’s disk. The implication of this is that no matter how small the object being imaged, even a single point of light doesnt form a point image.
Are natural pupil sizes limited by diffraction?
No, but quite close.
Consider a miotic pupil. Is it limited by diffraction?
It would allow for 6/6 VA, but not 6/3, and is therefore diffraction limited.
However, smaller pupil sizes reduce the aberrations present in the ocular system, and generally we see better in the bright vs dim. The tradeoff is in favour of less aberrations than drawing closer to the diffraction limit.
