Total Internal Reflection & Types and Uses of LASER

What is Total Internal Reflection?

Total internal reflection occurs when a light ray traveling through a denser medium hits the boundary of a less dense medium at an angle greater than the critical angle, causing the light to reflect entirely back into the denser medium.

Conditions for Total Internal Reflection

• The light must travel from a denser medium to a less dense medium.
• The angle of incidence must be greater than the critical angle.

The critical angle $\theta_c$ is given by:

$$\theta_c = \sin^{-1}\left( \frac{n_2}{n_1} \right)$$

where:

• $n_1$ is the refractive index of the denser medium.
• $n_2$ is the refractive index of the less dense medium.

Applications of Total Internal Reflection

• Optical Fibres: Used in telecommunications to transmit light signals over long distances with minimal loss.
• Periscopes: Utilized in submarines to observe objects above the water surface.

Understanding LASER

LASER stands for "Light Amplification by Stimulated Emission of Radiation." It is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

Types of LASER

• Solid-state LASER: Uses a solid medium like ruby or neodymium-doped crystals.
• Gas LASER: Uses a gas medium such as helium-neon or carbon dioxide.
• Semiconductor LASER: Also known as diode LASER, commonly used in laser pointers and optical drives.
• Liquid LASER: Uses a liquid medium, often dye-based, for tunable wavelengths.

Uses of LASER

• Medical: Used in surgeries, eye treatments, and skin therapies.
• Industrial: Employed in cutting, welding, and material processing.
• Communication: Used in fiber optic communication systems.
• Military: Utilized in range finding, targeting, and directed-energy weapons.