History
The Huygens Principle is also known as the Fresnel-Huygens Principle. This principle bears the names of two scientists: Augustin-Jean Fresnel, a French scientist, and Christiaan Huygens, a Dutch scientist. It is an analysis method that applies to wave propagation problems in the near-field and far-field limits, as well as near-field diffraction and reflection.
Definition
According to Huygens' principle, all points of a wave front of sound in a transmitting medium or of light in a vacuum or transparent medium can be regarded as new sources of wavelets that expand in all directions at a rate determined by their velocities.
The following wave propagation behaviour is highlighted by the Huygens Principle:
- Similarly to the primary source, secondary sources also produce wavelets.
- The common tangent on the wavelets in the forward direction at any given time gives the new wavefront.
- The wavefront is composed of the sum of the spherical wavelets.
Primary and Secondary Sources
Huygens proposed that light is fundamentally a wave that spreads through space, similar to waves in water or sound in air. As a result, light spreads out like waves from a source in all directions. A wavefront is the location of focuses that traveled far during an immovable span. As a result, the locus of focuses that light has gone through during a fixed timeframe may be a circle from some degree of wellspring of daylight.
When a primary wavefront is created, a secondary wavefront is also created for every primary wavefront. At the same time, every point on that wavefront will now act as a secondary source of light, generating more wavefronts. Light waves spread out in space in this way, creating secondary sources and wavefronts.
Huygens Principle and Diffraction
When light passes through an aperture, each point on the light wave within the aperture can be regarded as a source, resulting in a circular wave that propagates outward from the aperture. As a result, the aperture generates a new wave source that propagates as a circular wavefront. The intensity is higher in the center of the wavefront and lower at the edges. This explains the observed diffraction pattern and why no perfect image of the aperture is created on a screen. This phenomenon is common in everyday life.
Advantages and Disadvantages of Huygens Principle
Advantages:
- Huygens' concept established light reflection and refraction.
- Huygens established concepts such as light diffraction and light interference.
Disadvantage:
- Huygens' principle did not explain concepts such as light emission, absorption, and polarization.
- The photoelectric effect was not explained by the Huygens principle.
- One significant disadvantage is that the theory proposes luminiferous ether, an all-pervading medium required for light propagation. This was proven false in the twentieth century.
Things to Remember
- According to the Huygens Principle, each point of the wavefront is the source of secondary wavelets, which spread out in all directions at the speed of a wave.
- According to Huygens' principle, each point on the wavefront can also be viewed as a wellspring of secondary circular wavelets that spread out in the forward direction at the speed of light.
- In 1678, Huygens proposed Huygen's principle, which explains daylight and its properties.
- Huygens proposed that light is fundamentally a wave that spreads through space, similar to waves in water or sound in air.
- Huygen's theory established the reflection and refraction of sunlight.
- The photoelectric effect was not explained by Huygen's principle.
- One significant disadvantage is that the concept proposes luminiferous ether, an all-encompassing medium required for light propagation. This was proven false within the twentieth century.