Optics Unit 2 Flashcards
What is meant by the refractive index?
It compares the speed of light in a vacuum with the speed of light in a subastance.
What is the refractive index of air?
1
What is the cricital angle?
When the angle of refraction os 90⁰
When does total internal reflection occur?
When the angle of refraction is above the critical angle
What are the two requirements of total internal reflection
The angle of incidence must be larger than the critical angle
It has to be travelling from a more dense to a less dense material. Eg- glass to air
Why do fibre optic cables need cladding?
- To protect the fibres from damage
- To prevent multi path dispersion
- To prevent light rays from exiting the core so no energy loss
- To control the number of reflections
What is phase difference?
The relative distance of two waves between one point on one wave compared with the same point on the other wave
What is constructive interference?
When two waves reinforce and superpose
What is destructive interference?
When two waves cancel eachother and superpose
What are bright fringes?
They are created when reinforcement occurs
What are dark fringes?
They are formed by cancellation
What is the fringe spacing?
The distance between the middle of two bright or two dark fringes
What happens when light goes through the double slit and hits the screen?
The wave diffracts and where they are in phase they will reinforce creating bright fringes and where the waves are 180⁰ out of phase they will cancel out and create dark fringes.
What will the graph look like when the light hits the screen.
What are the conditions are there for path difference when two waves are in phase?
They are a whole number of wavelengths
What does the interference pattern for white light look like? Compare it to monochromatic light.
The bright fringes are larger as the wavelengths are different but the dark fringes are smaller
