OV1001 Optics Flashcards
What is light?
A form of radiant energy
Wave particle duality
What are the rules of geometrical optics
- Light travels in the form of rays that are coming from a source of light
- A ray of light travels in a straight line until it meets an optical boundary
What happens to light rays as it passes a diffuse surface?
Light rays scattered in all directions
What happens to light as it travels through a more optically dense medium?
It travels more slowly
What do closer wavefronts within glass mean?
Indicates light is travelling at a slower speed
What happens to wavefront as it enters a more optically dense medium?
Wavefronts has been tilted because of the uneven slowing down
What does a higher refractive index mean?
More dense material
What can prisms help treat?
Muscular imbalance
What happens when objects are viewed through a prism?
They are displaced towards the apex of the prism
What does the amount of displacement depend on?
Angle of the apex
Thickness of prism
If a prism is thicker what does that mean?
Stronger amount of correction
Displaces objects to a greater degree
What is dispersion?
White light refracting into different colours when shone through a prism
What happens to rays as they go from a low refractive index to a high one?
They refract towards the normal
What is the ideal optical system?
All rays converging to a single point
What does the paraxial approximation do?
Ignores rays that refract too far
Key feature for n=c/v
Always greater than 1
What is the principal of reversibility ?
If we swap the location of object and image, the system behaves in the same way
What is vergence?
Measure of how much a set of rays are diverging or converging
How do you know if an optical surface has power ?
If it has the ability to change the vergence upon refraction
What does it mean if you get reflection instead of refraction? (TIR)
- Light is travelling from a medium with higher refractive index to a medium with lower refractive index (i.e. n > n0)
- The angle of incidence i is greater than the critical angle of incidence, ic (i.e. i > ic).
Define centre of curvature?
The centre of curvature of a spherical surface is a point representing the centre of the sphere the surface would be part of, had the whole sphere been present
Define the first focal point
The point on the optical axis such that the object rays that meet or originate from this point will refract parallel to the optical axis
Define the second focal point
The point on the optical axis where the image rays meet if the object rays are parallel to the optical axis
Why is the thin lens approximation used
Allows us to ignore this change in vergence due to the displacement through the lens