Question

What is the difference between reflection and refraction?

Answer 1

Reflection
Reflection is the abrupt change in the direction of propagation of a wave that strikes the boundary between two different media. Most of the part of the incoming wave remains in the same medium. Assume the incoming light ray makes an angle ${\theta }_i$ with the normal of a plane tangent to the boundary. Then the reflected ray makes an angle ${\theta }_r$ with this normal and lies in the same plane as the incident ray and the normal.
Law of reflection: ${\theta }_i={\theta }_r$

Refraction
Refraction is the change in direction of propagation of a wave when the wave passes from one medium into another and changes its speed. Light waves are refracted when crossing the boundary from one transparent medium into another because the speed of light is different in different media. Assume that light waves encounter the plane surface of a piece of glass after travelling initially through the air as shown in the figure. The bending will happen according to laws of refraction:
$\frac{sini}{sinr}=\mu$
Where $\mu$ is known as refractive index and is basically the ratio of the speed of light in the first medium w.r.t second medium.