Refraction of light and Snell's Law

In this lesson, we will learn:

• Key terms in refraction
• Ray diagrams in refraction
• Solving Snell’s law problems

• Incident ray: The incoming ray of light
• Refracted ray: The transmitted ray of light into another medium
• Medium of incidence: The medium in which light travels before it strikes the boundary.
• Medium of refraction: The medium through which refracted ray travels.
• Point of incidence: The intersection of the incident ray and the boundary.
• Normal: An imaginary line is drawn perpendicular to the boundary at the point of incidence.
• Angle of incidence (< $i$ ): The angle between the NORMAL and the incident ray.
• Angle of refraction (< $r$): The angle between the NORMAL and the refracted ray.
• If the incident ray is perpendicular to the boundary the angle of incidence is ZERO, and the angle of refraction will also be ZERO.
• Snell’s law: The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, “n”

$\large n = \frac{sin \, \theta _{i} }{sin \, \theta _{r}},$

“n” is called the index of refraction

In the more general cases the Snell’s law can be written as :

• Index of refraction: Physical characteristics of matter which determines the extent to which light gets refracted.
• Optically dense medium: The medium in which the angle between the ray and normal is smaller is called the optically denser medium.
• The denser the medium the smaller the speed of light in that medium
• The denser the medium the bigger the value of “$n$”.
• The refracted ray bends TOWARDS the normal in optically denser medium