A Short Note on Wave Front and Wave Normal

Wave normal is the direction of propagation of light perpendicular to the surface of the wave front. Wave front is defined as the locus of all points that receive the disturbance of light simultaneously. Propagation of light depends on the wave front and the frequency of weave is determined by the wave normal. Wave surface refers to the sphere in which the source of light and distance travelled by the light wave arrive simultaneously. Wave front also refers to the surface in which the phase of light is constant. In the perpendicular wave front all the particles of the medium travel in the same motion.

What Is a Spherical Wave Front?

The point of source in the isotropic medium transfers light in 3 dimensions in which the wave fronts are spheres centred on the source of light. A spherical wave front occurs in the case when the observation point is very close to the point of the light source. In this wave front, the surfaces are at a common phase and the source of light is in the centre. Spherical waves propagated in an outward direction due to the spherical disturbance of light. In the spherical wave, the point of a source is denoted by the source of incident light.

Visit to know more about UPSC Exam Pattern

Explanation of Wave Normal

Wave normal refers to the line perpendicularly drawn to the surface at any point of a medium in the direction of propagation of the source. The direction of light is denoted by ray and wave normal is the direction of ray from the surface. Wave normal is the normal radiation of light in a certain period and phase. Wave normal is also defined as the 90-degree propagation of light due to the nature of distance from the surface and light source.

Explanation of Locus

A locus is the combination of all points that forms a curve or surface to satisfy the condition of spherical waves or other special conditions. The wave front is the locus of all points in the same phase in which propagation of light occurs. The Distance between the locus point and the source of light is defined as the wave normal.

Read about How to Prepare for UPSC without Coaching

Propagation of Light

Propagation of light is defined as the transfer of energy from one surface to another by using the electromagnetic equation. Three types of propagation generally occur such as direct propagation through space, propagation through medium and reflection of light from a mirror. The speed of light in open space is constant and it depends on the wavelength of the incident photons on the surface. The energy transmitted from the photon is converted to the free-electron for releasing electromagnetic waves in a certain frequency of light. The law of rectilinear propagation states that the propagation of light is a straight line in a homogeneous medium.

Types of Propagation

• Direct propagation: Light is propagated directly from the source through open space.
• Propagation through a medium: Light is propagated through the medium and the density of the surface determines the level of energy produced from  the medium.
• Reflection from a mirror: This type of propagation occurs when light is reflected from the mirror and the frequency of the wave depends on the smoothness of the surface.
• In the direct propagation, the speed of the wave can be equal to the speed of the light in space.

Also read Tips for UPSC Preparation

Characteristics of Propagation of Light

The intensity of the propagated light depends on the nature of the source and the direction of light propagation. The motion of the source depends on the direction of the wave normal and the observation point. Light propagation is affected by reflection, absorption, fluorescence refraction and scattering. Refraction of light from the surface changes the direction of propagation and it is determined by the angle. In the propagation of light, the amplitude of a wave depends on the electromagnetic density.

Conclusion

The above study indicates that the propagation of light can occur in three different types and the frequency of propagation depends on the nature of the source. Wave normal is the perpendicular drawn line from the surface of the locus of all points and the source of light. Propagation of light is defined as the reflection of energy from the surface in the form of free electrons. The oscillation of electric and magnetic fields changes with the time and speed of the intensity of light. The principle of light propagation states that the propagation occurs due to the internal reflection of light.