Lecture 2 - Refraction Flashcards
What is refraction
when a wave or light ray moves from one medium to another e.g. air/glass/water causing speed and direction to change
What does refraction cause
Bending of light - wavefront tilted
= changes direction
What happens when light travels from a fast medium to a slow medium
e.g. air to glass/water
Refractive index of glass HIGHER than air
SLOWS down, ray of light TOWARDS normal
Angle of refraction < angle of incidence
What happens when light travels from a slow medium to a fast medium
e.g. glass/water to air
SPEEDS UP
ray of light AWAY from normal
Angle of refraction > angle of incidence
Whats the rule for rays and wavefronts
Rays and wavefronts are 90 degrees/ perpendicular to each other
How do ripples work
Stone in pond
Starts circular and steep
Less steep as wavefronts move away
Eventually flat and parralel lines, less circular large distance away
Where do ripples of water travel
Outwards
Away from where rock fell in water
What is the refractive index formula
n = c/v c = speed of light in vaccum v = speed of light in medium
is n negative or positive number
positive
what is snells law formula
n sin i = n' sin i' n = refractive index before refraction i = angle of incidence n' = refractive index after refraction i' = angle of refraction
what is prism
correct squint - moves object so it goes onto fovea
How to correct squints
- Object moved towards angle of prism
- Control how much it moves by how big angle is
- Also swap direction - rotate it
Dispersion in rainbow
different wavelengths dispersed = rainbow = different colours
shine white light
Does it travel faster or slower in middle of lens and why
slower
because thicker
what part of wavefront hits lens first
middle before edges