Refraction is the bending of light when it passes from one medium to another.
When light goes from a rarer medium to a denser medium, it bends towards the normal.
When it goes from a denser medium to a rarer medium, it bends away from the normal.
If the light falls at a ninety-degree angle, it passes without bending.
Important Definitions
Refractive Index
The refractive index of the second medium with respect to the first medium.
Definition: μ₂₁ = V₁/V₂
Speed and Wavelength
The refractive index can also be defined in terms of speed or wavelength.
Example: If the refractive index of glass is 1.5 and the speed of light in air is 3 × 10^8 m/s, the speed of light in the glass will be 2 × 10^8 m/s.
Important Questions
Calculating the speed of light with the refractive index of glass.
Definition and reason for refraction.
Calculating the refractive index between different media.
Questions based on the principle of reversibility.
Laws of Refraction
Law of Refraction: sin i/sin r = constant
Another definition of refractive index: μ₂₁ = λ₁/λ₂ = sin i/sin r
Refraction Through Glass Slab
After refraction through a glass slab, the emergent rays are parallel and slightly displaced, known as lateral displacement.
Lateral displacement depends on:
Refractive index
Angle of incidence
Thickness of the slab
Wavelength of light
Relationship between wavelength and displacement in colors: Red color displacement is the least and violet is the most.
Refraction Through Glass Prism
Key angles related to refraction in a prism:
Angle of incidence
Angle of emergence
Angle of prism
Angle of deviation
Key formulas:
a = r₁ + r₂
δ = i + e - a
Factors on which the angle of deviation depends:
Angle of prism
Angle of incidence
Refractive index of the prism
Total Internal Reflection
When light goes from a denser to a rarer medium and the angle of incidence is greater than the critical angle, total reflection occurs.
Important definitions:
Critical angle: The angle at which refraction is 90 degrees.
Examples of total internal reflection in a prism.
Conditions for total internal reflection:
Light should be going from a denser to a rarer medium.
The angle of incidence should be greater than the critical angle.
Special Questions
Analyzing the path of light in different types of prisms.
Understanding the concept of the critical angle and total internal reflection.
Conclusion
A thorough understanding and calculations of refraction and its various aspects such as refractive index, refraction through a glass slab and prism, and total internal reflection.