Physics - Reflection and Refraction
OCR A-Level Physics 2022
Labelling a reflection diagram
What is missing?
What is missing?
What is missing?
What is missing?
What is missing?What is the Law of Reflection?
On a smooth plane, the angle of incidence is equal to the angle of reflection.
Labelling a refraction diagram
What is missing?
What is missing?
What is missing?
What is missing?
What is missing?Why refraction happens
Why does refraction occur?
Because the wave changes speed when it passes from medium to another.
What is partial reflection?
A slight reflection off a surface that a wave is refracted through.
If a wave speeds up when it passes into a new medium, what happens to the angle of refraction?
It increases.
If a wave slows down when it passes into a new medium, what happens to the angle of refraction?
It decreases.
Wavelength changes during refraction and reflection
What happens to the wavelength of a wave if it speeds up when being refracted?
It increases.
What happens to the wavelength of a wave if it slows down when being refracted?
It decreases.
What happens to the wavelength of a wave if it bends away from the normal when being refracted?
It increases.
What happens to the wavelength of a wave if the angle of refraction decreases when passing into a new medium?
It decreases.
What happens to the wavelength of a wave when it is reflected?
It stays the same.
How can the frequency of a refracted wave stay the same if the wavelength changes?
The wave speed changes to compensate.
The refractive index and Snell’s law
What is the formula for the refractive index $n$ given the speed of light in a vacuum $c$ and the speed of light in the material $v$?
Informally, what does the refractive index of a material tell you?
How much you divide the speed of light by to get the speed inside the material.
Critical angle
What is the formula for the refractive index $n$ of a material in terms of its critical angle $c$?
Dispersion: refractive index depends on wavelength
Why is Snell’s law
\[n _ 1 \sin\theta _ 1 = n _ 2 \sin\theta _ 2\]
a lie?
Because $n$ is actually a function of wavelength $n(\lambda)$.
Why is the refractive index of a material actually a function of the wavelength, $n(\lambda)$?
Because different wavelengths of light travel at different speeds.