16. Define the term, ‘Critical Angle’. What is meant by ‘total internal reflection’ ? State two essential conditions for total internal reflection to take place. With the help of a ray diagram, illustrate an application of total internal reflection. OR?

Question

Answer

§ The angle of incident beyond which a light ray from denser medium to rarer medium no more refract but reflect to same medium is known as critical angle.

§ The complete reflection of light reaching a interface with a less denser medium when the angle of incidence is greater than critical angle is known as total internal reflection.

§ The two essential conditions for total internal reflection are: -
i)The ray should be traveling from a denser to rarer medium.
ii) The angle of incident should be greater than critical angle.

§ Application of total internal reflection are in microscope, binoculars etc.

That's all🙂

Answer

》Critical angle:The angle of incidence at which the light ray travelling from denser to rarer medium grazes the interface ia called critical angle.

》Total Internal Reflection (TIR):When the angle of incidence is greater than the critical angle the the light ray gets reflected into the denser medium i.e ..light never enters the rarer medium .This phenomenon is called Total Internal Reflection

》2 Essential conditions for TIR:

1.Light ray must travel from denser to rarer medium

2.Angle must be greater than the critical angle.

》Applications of TIR:

1.Brilliance of diamonds

2.Optical fibres

Answer

Definition of Critical Angle:

The critical angle is defined as the angle of incidence in a medium at which the angle of refraction in the second medium is 90 degrees. Beyond this angle, the light undergoes total internal reflection instead of refraction.

Definition of Total Internal Reflection:

Total internal reflection occurs when a light ray traveling from a denser medium to a less dense medium strikes the boundary at an angle of incidence larger than the critical angle. Instead of refracting into the second medium, the light ray is reflected back into the denser medium.

Conditions for Total Internal Reflection:

For total internal reflection to occur, two conditions must be met:

1. The light ray must be traveling from a denser medium to a less dense medium. This means that the angle of incidence must be greater than the critical angle.

2. The angle of incidence must be larger than the critical angle. The critical angle can be calculated using the relationship sin(critical angle) = n2/n1, where n1 and n2 are the refractive indices of the two media.

Application of Total Internal Reflection:

One practical application of total internal reflection is in optical fibers. Optical fibers are thin, transparent strands of glass or plastic that are used to transmit light signals over long distances. They work based on the principle of total internal reflection.

When light is introduced into one end of an optical fiber at an angle greater than the critical angle, it undergoes total internal reflection as it travels through the fiber. The light is continuously reflected off the walls of the fiber due to the total internal reflection, allowing it to propagate along the length of the fiber without significant loss of intensity.

At the receiving end of the fiber, the light can be extracted and used for various purposes, such as communication or data transmission. The ability of optical fibers to transmit light signals over long distances with minimal loss is a result of the total internal reflection phenomenon.

In the diagram below, a light ray entering the optical fiber at an angle greater than the critical angle undergoes total internal reflection. The ray is continuously reflected back into the fiber, allowing it to propagate along the length of the fiber.

[Diagram]

This application of total internal reflection in optical fibers is widely used in telecommunications, internet connectivity, medical imaging, and various other fields where efficient and long-distance transmission of light signals is required.

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