# Physics - Reflection and Refraction

> Source: https://ollybritton.com/notes/a-level/physics/topics/reflection-and-refraction/ · Updated: 2024-08-25 · Tags: school, physics, waves, year-1

##### ![PHOTO REFLECTION NO NORMAL](reflection-no-normal.jpg) What is missing??
![PHOTO REFLECTION](reflection.jpg)

##### ![PHOTO REFLECTION NO INCIDENT](reflection-no-incident.jpg) What is missing??
![PHOTO REFLECTION](reflection.jpg)

##### ![PHOTO REFLECTION NO REFLECTION](reflection-no-reflection.jpg) What is missing??
![PHOTO REFLECTION](reflection.jpg)

##### ![PHOTO REFLECTION NO INCIDENT ANGLE](reflection-no-incident-angle.jpg) What is missing??
![PHOTO REFLECTION](reflection.jpg)

##### ![PHOTO REFLECTION NO REFLECTION ANGLE](reflection-no-reflection-angle.jpg) What is missing??
![PHOTO REFLECTION](reflection.jpg)

##### What is the Law of Reflection??
On a smooth plane, the angle of incidence is equal to the angle of reflection.

##### ![PHOTO REFRACTION NO INCIDENT](refraction-no-incident.gif) What is missing??
![PHOTO REFRACTION](paste-e95e1d83acf5bc8deb782e358aaedd25c2473ccd.jpg)

##### ![PHOTO REFRACTION NO INCIDENT ANGLE](refraction-no-incident-angle.gif) What is missing??
![PHOTO REFRACTION](paste-e95e1d83acf5bc8deb782e358aaedd25c2473ccd.jpg)

##### ![PHOTO REFRACTION NO REFRACTION](refraction-no-refraction.gif) What is missing??
![PHOTO REFRACTION](paste-e95e1d83acf5bc8deb782e358aaedd25c2473ccd.jpg)

##### ![PHOTO REFRACTION NO REFRACTION ANGLE](refraction-no-refraction-angle.gif) What is missing??
![PHOTO REFRACTION](paste-e95e1d83acf5bc8deb782e358aaedd25c2473ccd.jpg)

##### ![PHOTO REFRACTION NO EMERGENT](refraction-no-emergent.gif) What is missing??
![PHOTO REFRACTION](paste-e95e1d83acf5bc8deb782e358aaedd25c2473ccd.jpg)

##### 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 downwhen it passes into a new medium, what happens to the angle of refraction??
It decreases.

### 2021-03-04
##### 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.

##### What happens to the speed of a water wave in deep water??
It increases.

### 2021-04-28
##### 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 $v$??
$$
n = \frac{c}{v}
$$

##### What is Snell's Law??
$$
n_1 \sin \theta_1 = n_2 \sin \theta_2
$$
##### What's the typical range for refractive indicies??
$$
1 \to 2.5
$$

##### 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.

### 2021-05-11
##### What is the formula for the refractive index $n$ of a material in terms of its critical angle $c$??
$$
n = \frac{1}{\sin c}
$$

### 2021-10-09
##### 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.

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