REFRACTION OF LIGHT

Refraction of Light

Definition

  • Refraction of Light: The bending of light when it travels from one medium to another at an angle.

Key Differences

  • Reflection: The bouncing off of light.

  • Refraction: The bending of light at the interface between two media.

Snell's Law

  • States the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.

Laws of Refraction

  1. The incident ray, refracted ray, and normal at the point of incidence lie in the same plane.

  2. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.

Refractive Index

  • Definition: The ratio of the sine of the angle of incidence to the sine of the angle of refraction for light traveling from air to a substance.

Sample Calculations

  1. Refractive Index from Water to Glass:

    • Given indices: Water (4/3), Glass (3/2)

    • Calculated index: [ n_{wg} = \frac{3/2}{4/3} = 1.13 ]

  2. Angle of Refraction using Snell's Law:

    • Given: Angle of incidence = 40°, refractive index of glass = 1.7

    • Calculation: [ \sin(r) = \frac{\sin(40)}{1.7} ] leading to [ r = 22.2° ]

  3. Finding Critical Angle:

    • Critical angle for glass with refractive index 1.5: [ C = \sin^{-1}(\frac{1}{n}) = \sin^{-1}(0.6667) ] results in [ C = 41.81° ]

Total Internal Reflection

Definition

  • The critical angle is the angle of incidence in the denser medium for which the angle of refraction in the less dense medium is 90°.

Conditions for TIR

  1. Light must travel from a denser to a less dense medium.

  2. The angle of incidence must be greater than the critical angle.

Applications of Total Internal Reflection

  1. Optical Fibres: Used for medical instruments to view internal organs.

  2. Prismatic Periscopes: Used for navigation and observation.

Dispersion of Light

  • Definition: The splitting of white light into its constituent colors due to varying refractive indices for different wavelengths.

Key Terms

  • Wavelength: The distance between successive peaks of a wave.

  • Frequency: How often the wave oscillates per unit time.