Question

Explain the concepts of reflection, refraction (Snell’s Law), and total internal reflection using ray diagram.

Answer 1

Reflection

When light falls on an object, some of it bounces off the object. The bouncing off of light at a surface is called reflection. All surfaces reflect light. How well a surface reflects light depends upon the nature of the surface. Shiny, smooth surfaces such as a mirror reflect light better than dull, rough surfaces such as a wall or a sheet of paper.

Laws of reflection :

1. Incident ray , Normal and reflected ray all lie in same plane.

2. Angle of incedence is equal to angle of reflection

refraction (Snell’s Law)

In optics, refraction is a phenomenon that often occurs when waves travel from a medium with a given refractive index to a medium with another at an oblique angle. At the boundary between the media, the wave's phase velocity is altered, usually causing a change in direction. Its wavelength increases or decreases but its frequency remains constant

Snell's Law : When light passes from one transparent medium to another, it bends according to Snell's law which states:

Ni * Sin(Ai) = Nr * Sin(Ar),

where:
Ni is the refractive index of the medium the light is leaving,
Ai is the incident angle between the light ray and the normal to the meduim to medium interface,
Nr is the refractive index of the medium the light is entering,
Ar is the refractive angle between the light ray and the normal to the meduim to medium interface.

total internal reflection :

Total internal reflection happens when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle.