# What happens when the incident angle is equal to the critical angle?

**angle**of

**incidence**is

**equal to the critical angle**, the

**angle**of refraction is

**equal**to . If the

**angle**of

**incidence**is bigger than this

**critical angle**, the refracted ray will not emerge from the medium, but will be reflected back into the medium. This is called total internal reflection.

Hereof, what happens when the incident angle is greater than the critical angle?

When the **angle** of **incidence** in water reaches a certain **critical** value, the refracted ray lies along the boundary, having an **angle** of refraction of 90-degrees. For any **angle** of **incidence greater than the critical angle**, light will undergo total internal reflection.

Subsequently, question is, what is critical angle in total internal reflection? **Total internal reflection** takes place when the **angle** of incidence for the light ray is greater than the so-called **critical angle**. The **critical angle** is defined as the **angle** of incidence that provides an **angle** of refraction of 90-degrees.

In this way, how does Snell's law calculate critical angle?

The **critical angle** can be **calculated** from **Snell's law** by setting the refraction **angle** equal to 90°. For any **angle** of incidence less than the **critical angle**, part of the incident light will be transmitted and part will be reflected.

What is critical angle formula?

The **critical angle** = the inverse function of the sine (refraction index / incident index). The **equation** is: θ_{crit} = sin^{-}^{1}(n_{r}/n_{i}) We have: θ_{crit} = The **critical angle**.