Huygen’s principle

Explain Huygen’s principle. In this topic we will discuss what is Huygen’s principle and its applications.

Huygens’ Principle

Huygens’ principle states that every point on a wavefront acts as a source of secondary wavelets that spread out in all directions at the speed of the wave. The new wavefront is the forward envelope of these secondary wavelets.

Explanation of Huygens’ Principle

According to Huygens’ principle:

1. Every point on an existing wavefront acts as a source of secondary wavelets.
2. These secondary wavelets spread in all directions through the medium at the speed of the wave.
3. After a certain time, a common tangent surface touching the forward edges of all these wavelets forms the new wavefront.

To know about the wavefront click here-

https://youtu.be/2Fhm5mJMKNY

Applications of Huygens’ Principle

Huygens’ principle helps explain:

• Reflection of light: Why light changes direction when it reflects from a surface.
  • Refraction of light: Why light bends when it passes from one medium into another.
  • Diffraction of light: How waves spread around obstacles and through narrow openings.

Mathematical Relation

If a secondary wavelet travels with speed $v$ for time $t$, its radius is

$$\boxed{{\displaystyle r=vt}}$$

where: v is the velocity of wave ant t is the time taken.