# Wave equations

As is always the case in Physics, there are plenty of wave equations you need to know for the exam!

## v=fλ

No explanation necessary - just plug in the right numbers.

## f=^{1}⁄_{T}

^{1}⁄

_{Wave period (s)}

The period of oscillation is the amount of time it takes for a whole wavelength to pass a point.

## Refractive index: n=^{c}⁄_{v}

^{speed of light in a vacuum}⁄

_{speed of light in the material}

As explained elsewhere, every material has a refractive index - which is a ratio of the speed of light through a material as compared to the speed through a vacuum.

## Critical angle: sinC=^{n1}⁄_{n2}

^{refractive index of outside material}⁄

_{refractive index of inside material}

The critical angle is the minimum angle a ray of light needs to hit the boundary of a material with, in order to totally reflect internally. This equation gives the angle in degrees.

For total internal reflection to be possible, the refractive index of n_{1} must be lower than that of n_{2}

## Double slit formula: λ=^{ax}⁄_{D}

^{slit separation x fringe separation}⁄

_{distance to screen}

This equation applies to Young's double slit experiment on the diffraction patterns page.