Ray Optics

The study of the rays of light is known as ray optics. A ray of light travels in the same direction as it came from. An imaginary straight line is drawn from the source to understand the propagation direction.

The intensity of light at various wavelengths is different, and it depends on the material through which it is being transmitted. It causes rays to bend through glass, water, or air. 

There will be interference patterns (beams) with more strength in some places than others at any given cross-sectional area. 

Light and its Optical Properties

The laws of light explain its behaviour. Light is a transverse electromagnetic wave, meaning that the particles oscillating are perpendicular to each other, i.e., the propagation direction is perpendicular to their motion. 

In optics, this wave is described as a simple plane wave. However, any absorption effect or polarisation state may be present within those waves. Therefore, there could be more than one ‘real’ optical beam being emitted by an object in some cases – such as laser light.

Reflection

Reflection happens when a light ray hits a surface and bounces back. The light ray which hits the surface is called an incident ray, and the ray that reflects is known as a reflected ray. It is normal if the incident and reflected rays are drawn perpendicular to the surface.

As shown in the diagram above, the angle at which the incident ray hits the surface is known as the angle of incidence, and the angle at which the reflected ray leaves the surface is known as the angle of reflection.

Refraction

The deviation from the straight path of light is called refraction. The angle of refraction is the angle formed by the refracted ray and the normal, determined by Snell’s Law.

Refraction occurs when an electromagnetic wave encounters a boundary between two mediums with different refractive indices. The incident ray is bent towards the normal, whereas the reflected and refracted rays have deflection directions from that of incidence.

It causes a displacement in the wave propagation direction. The angle varies with degree along the path: α and depends on separation Δ. Maximum deviation occurs when n1 = 1, and then an extra phase shift is added because of twice deviated path length (path difference). 

Total Internal Reflection

Total internal reflection happens when waves from one medium to another are entirely reflected into the first medium and not refracted to the second medium. The second medium’s wave speed is faster than the first medium, and the interface waves are oblique

Real Image and Virtual Image

Real Image: After a mirror reflection, light rays meet at a point to produce real images.

Virtual Image: A virtual image appears to form behind a mirror. However, in reality, there is no picture behind the mirror. Virtual images are formed when light rays are reflected.

Ray Diagram of Convex and Concave Lens

If two transparent spheres are joined, spherical lenses can be made. There are two types of spherical lenses, and it is possible to create concave and convex lenses by combining two spherical surfaces that bend inward and outward, respectively.

Convex lenses are called converging lenses because the rays converge upon contact with the convex lens. Concave lenses are diverging lenses as the rays diverge upon contact with the concave lens.

Collimated Beam

Electromagnetic radiation or a collimated light beam or other parallel rays spread very little while travelling. As there is no separation, a perfectly collimated light beam never disperses. However, diffraction prevents the formation of such rays.

Conclusion

Optics is the study of light, and it is possible to divide the study of optical phenomena into three main categories – ray, wave, and quantum optics. 

Ray optics, or geometrical optics, describe light propagation that uses rays and transmits the light energy from one point to another in an optical device via a ray in a specific direction. 

Geometric optics assume that rays travel straight before reaching a surface. 

When a ray hits a surface, it may bend, but it always travels forward in a straight line. There are two fundamental laws in geometrical optics – refraction and refraction. 

Visible light is a type of electromagnetic wave with a specific wavelength.