# Optics Formulas

Optics is the branch of physics that tells how the light behaves, its properties and its interactions. There are many formulas in optics. Some of them are,

**Refractive index,**

n = $\frac{Speed \ of \ light \ in \ vacuum}{Speed \ of \ light \ in \ a \ medium}$ = $\frac{c}{v}$

**Snell's law of refraction:**If n

_{1}and n

_{2}are the refractive indexes of medium 1 and medium 2 and $\theta_1$ is the angle of the incident ray and $\theta_2 is the angle of refracted ray.

**The snell's law is given by,**

n

_{1}sin $\theta_1$ = n_{2}sin $\theta_2$.**The critical angle is given by,**

sin $\theta_c$ = $\frac{n_1}{n_2}$.

**Mirror formula,**

$\frac{1}{u}$ + $\frac{1}{v}$ = $\frac{1}{f}$.

Where,

u is image distance,

v is the object distance,

f is the focal length.

Where,

u is image distance,

v is the object distance,

f is the focal length.

**Magnification,**

m = $\frac{v}{u}$ = $\frac{v-f}{f}$ = $\frac{f}{u-f}$,

or

or

m = $\frac{I}{O}$.

**Thin lens formula,**

$\frac{1}{f}$ = $\frac{1}{v} - \frac{1}{u}$

Where, u is image distance, v is object distance.

**The power of lens is given by,**

P = $\frac{1}{Focal\ length}$.

**The equivalent focal length of two lens in contact is given by,**

$\frac{1}{F}$ = $\frac{1}{f_1} + \frac{1}{f_2}$.

Where,

f

_{1}is the focal length of the lens 1,

f

_{2}is the focal length of the lens 2,

F is equivalent focal length.

_{.}

_{}

_{}