Total Internal Reflection Quiz

Total Internal Reflection

• Total internal reflection occurs when light travels from a denser medium to a less dense medium.
• When light travels from a denser medium to a less dense medium, it bends away from the normal.
• Critical Angle: The angle of incidence at which the refracted ray makes an angle of 90 degrees with the normal is called the critical angle.
• If the angle of incidence is greater than the critical angle, the light is totally reflected back into the denser medium.
• Conditions for Total Internal Reflection:
  • The light must be traveling from a denser medium to a less dense medium.
  • The angle of incidence must be greater than the critical angle.

Examples of Total Internal Reflection

• Optical fibers: Fiber optic cables use total internal reflection to transmit light signals over long distances. Light is confined within the core of the fiber by total internal reflection at the boundary with the cladding.
• Prisms: Total internal reflection is used in prisms to create a 90-degree or 180-degree deviation of light, allowing for use in binoculars and periscopes.
• Diamonds: The brilliance of diamonds is due to total internal reflection. Light entering a diamond is reflected internally multiple times before exiting, giving diamonds their sparkle.
• Water droplets: When sunlight enters a water droplet at an angle greater than the critical angle, it undergoes total internal reflection and creates a rainbow.
• Mirages: Mirages occur when light passes through layers of air with different temperatures. The hotter air near the ground has a lower refractive index than the cooler air above it. When light traveling through the cooler air hits the boundary with the warmer air at an angle greater than the critical angle, it undergoes total internal reflection, creating the illusion of a reflection from a wet surface.

Factors affecting the Critical Angle

• Refractive indices of the two mediums: The critical angle depends on the refractive indices of the two mediums. The higher the difference in refractive indices, the smaller the critical angle.
• Angle of incidence: The critical angle is the angle of incidence at which the refracted ray makes an angle of 90 degrees with the normal.
• Wavelength of light: The critical angle also depends on the wavelength of light. Shorter wavelengths of light (such as blue light) have a higher refractive index than longer wavelengths (such as red light), so the critical angle is smaller for blue light.