What are the laws of refraction? Explain with the help of ray diagrams

The laws of refraction, also known as Snell’s Laws, describe how light behaves when it passes from one medium to another. These laws are fundamental in understanding how light bends when traveling through different materials.

Laws of Refraction

  1. First Law of Refraction (Snell’s Law): The incident ray, the refracted ray, and the normal to the surface of separation between the two media all lie in the same plane.

    Explanation: This law means that all three vectors (incident ray, refracted ray, and the normal line) are coplanar, i.e., they all lie on the same flat surface.

  2. Second Law of Refraction (Snell’s Law of Refraction): The ratio of the sine of the angle of incidence (θ₁) to the sine of the angle of refraction (θ₂) is constant for a given pair of media. This constant is called the refractive index (n) and is specific to the pair of media involved.

    Mathematically:

    sin⁡θ1/sin⁡θ2=n2/n1

    Where:

    • θ₁ is the angle of incidence (angle between the incident ray and the normal).
    • θ₂ is the angle of refraction (angle between the refracted ray and the normal).
    • n₁ is the refractive index of the first medium.
    • n₂ is the refractive index of the second medium.

Snell’s Law – Mathematical Application:

For the two media (like air and water), Snell’s Law gives us a mathematical relationship between the angles and refractive indices:

sin⁡θ1/sin⁡θ2=n2/n1

If you know the refractive index of the two media and one of the angles (either incidence or refraction), you can calculate the other angle. For example:

  • If light travels from air (n₁ = 1) to water (n₂ ≈ 1.33) with an angle of incidence of 30°, you can calculate the angle of refraction using Snell’s Law.

Related Questions:

  1. What is reflection of light? Define the following terms: Incident ray, reflected ray, normal, angle of incidence, and angle of reflection. Describe the laws of reflection.
  2. What are different spherical mirrors? Define different terms involved in spherical mirrors.
  3. Why is a concave mirror called a converging mirror? Why is a convex mirror called a diverging mirror?
  4. Define the principal focus of convex and concave mirrors. Define focal length. Which mirror has a positive focal length? Which has a negative focal length and why?
  5. What is the spherical mirror formula? Also, write down the sign conventions for the spherical mirror formula.
  6. Differentiate between real and virtual images. What are three basic rays by which we can draw a ray diagram to form an image by a spherical mirror?
  7. What is refraction of light? Show by ray diagram how light bends when it travels from rare to denser medium and from denser to rare medium. Define the refractive index of a medium. What are its different formulae?
  8. Explain the phenomenon of total internal reflection. What are necessary conditions to perform total internal reflection? Derive the formula for the refractive index of a medium in terms of the critical angle.
  9. What is optical fibre? How does light travel through it? Explain.
  10. What is a lens? What are its types? Define the basic terminologies of lenses.
  11. When you look at the front side of a polished spoon, your image is inverted, and from the back of the spoon, your image is erect. Explain why?
  12. Which mirror is used by girls for makeup and why?
  13. Why are large convex mirrors fixed at blind turns of mountains?
  14. Which mirrors are used for the rear view of vehicles and why?
  15. If a person is walking in a pool, why do his legs appear shorter in water?
  16. Why do diamonds sparkle brightly?
  17. When white light passes through a prism, it disperses into its seven colors. Why does dispersion take place in a prism?
  18. A magnifying glass can burn the paper. How is it possible?
  19. Your grandfather uses spectacles to read a newspaper. You see through the spectacles and observe that objects behind it were inverted. Why was it so observed?
  20. Under what condition does a convex lens nearly act as a diverging lens?