Refraction of Light at Plane Surfaces

1. Laws of Refraction

1.1. Given by the Dutch Scientist - Willebrod Snell

1.2. 1.) The Incident ray, the Refracted ray and the Normal at the point of Incidence , all lie on the same plane.

1.3. 2.) The ratio of the sine of the angle of Incidence i to the sine of the angle of Refraction r is constant for a given pair of media

1.4. sin i / sin r = constant 1u2, where constant 1u2 is called the Refractive index

2. Effect on Speed , Frequency and Wavelength

2.1. Rarer to Denser=Speed of light decreases

2.2. Denser to Rarer=Speed of light increases

2.3. Frequency depends on source of light , hence does not change on refraction

2.4. Wavelength=V/f

2.5. Rarer to Denser-Wavelength Decreases

2.6. Denser to Rarer-Wavelength Increases

3. Refractive Index

3.1. Definition

3.2. Has no unit

3.3. u = Speed of light in vacuum or air (c) / Speed of light in that medium (V)

3.4. Refractive Indices of some common substances

3.5. 1u2 = Speed in medium 1 / Speed in medium 2

3.6. 1u2 = V1 / V2 = (c/V2) / (c/V1) = u2 / u1

3.7. Factors affecting Refractive Index

3.7.1. Nature of the medium

3.7.2. Physical Conditions

3.7.3. Color or Wavelength of light

4. Refraction

4.1. Definition

4.2. Partial Reflection and Partial Refraction

4.3. Refraction from rarer to denser medium

4.3.1. Bends towards the normal

4.3.2. Angle r* < Angle i*

4.3.3. Angle of Deviation = i - r

4.4. Refraction from denser to rarer medium

4.4.1. Bends away from the normal

4.4.2. Angle r* > Angle i*

4.4.3. Angle of Deviation = r - i

4.5. Refraction at normal incidence

4.5.1. Passes undeviated . Traces the Normal

4.5.2. Angle i* = Angle r* = 0*

4.5.3. Angle of Deviation = 0*

5. Cause of Refraction

5.1. It is because of the change in speed of light from one transparent medium to another transparent medium.

5.2. There is a Deviation in the incident ray due to the speed of light.

5.3. Exception: For normal incidence , speed of light changes but the direction of light does not change

6. Principle of Reversibility

6.1. States path of light ray is reversible

6.2. 1u2 = sin i / sin r

6.3. 2u1 = sin r / sin i

6.4. 1u2 x 2u1 = 1

7. Refraction of light through a rectangular glass slab experiment