Color, Light & Vision Cheat Sheet

Key Facts

• Light travels fastest in a vacuum at $c = 3.00 \times 10^8\ \text{m/s}$ and slower in materials such as water or glass.
• Wave speed is related to frequency and wavelength by $v = f\lambda$.
• The law of reflection states that $\theta_i = \theta_r$, where both angles are measured from the normal line.
• The index of refraction is $n = \frac{c}{v}$, so a larger $n$ means light travels more slowly in that material.
• Snell's law is $n_1\sin\theta_1 = n_2\sin\theta_2$ for light bending between two transparent materials.
• For thin lenses and curved mirrors, the image equation is $\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}$.
• Magnification is $M = \frac{h_i}{h_o} = -\frac{d_i}{d_o}$, where a negative value means the image is inverted.
• White light contains many wavelengths, and visible light is roughly $400\ \text{nm}$ to $700\ \text{nm}$.

Vocabulary

Wavelength

Wavelength is the distance from one wave crest to the next, often represented by $\lambda$.

Frequency

Frequency is the number of wave cycles passing a point each second, measured in hertz, or $\text{Hz}$.

Reflection

Reflection is the bouncing of light off a surface, following $\theta_i = \theta_r$.

Refraction

Refraction is the bending of light when it changes speed as it enters a different material.

Primary Colors of Light

The primary colors of light are red, green, and blue, and they combine additively to make other colors.

Retina

The retina is the light-sensitive layer at the back of the eye where rods and cones detect images.