Refraction Of Light

What is Refraction• The velocity of electromagnetic energy in a vacuum is commonly

known as the speed of light (Index of 1 - Velocity of 300,000 km per second).

• Light travels slower in other materials such as glass (Index of 1.5 - Velocity of 200,000 km per second).

• Light travelling from one material to another changes speed, resulting in a change in direction of travel. This deflection is known as refraction.

• Different wavelengths of light travel at different speeds in an identical medium. This variation of velocity with wavelength has an intergral role in fiber optics.

• Also of particular importance is that the index of glass can be changed by controlling its composition.

• If one were to stand on a pier and look directly down at a fish, the light would not be refracted, so the fish would be in its apparent position, but if one were to view that same fish at an angle, refraction of light would occur and the fish would appear closer to the surface. What appears to be a straight line from the fish to the eye is actually a line with a bend where the light passes from water into air and is thus refracted resulting in the fish actually being deeper in the water than it appears.

• The normal is an imaginary line perpendicular to the interface of the two materials.

• The angle of incidence is the angle between the incident ray and the normal.

• The angle of refraction is the angle between the refracted ray and the normal.

Applications of Refraction

• Lens: Refraction is at the core of the functioning of a lens. A lens uses refraction for image formation which is used for several purposes such as magnification. Our eye is also a lens where what we see is projected on our retina. Here also refraction is used to form the image on the retina. Uses of a lens in our daily life are galore like magnifying glasses, eye glasses, contact lenses.

• Prism: A prism uses refraction to form a spectrum of colors from an incident beam of light.A prism can be used to break light up into its constituent spectral colours (the colors of the rainbow). Prisms can also be used to reflect light, or to split light into components with different polarizations.

• Mirage: A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. Some common examples are water bodies in a desert and wet roads on a hot sunny day.

Real Life examples of Refraction

• Twinkling and Shimmering: Earth’s atmosphere consists of flowing masses of air of varying density and temperature that causes the refractive index to vary slightly from one region of the atmosphere to another. This causes refraction of light rays coming from stars and hence the stars appear twinkling.

• Ophthalmology: Refraction finds a special place in ophthalmology where it is used as a clinical test in which a phoropter may be used to determine the eye's refractive error and hence to determine the corrective measures.

• Other common applications are telescopes, microscopes, etc.