The correct answer is the Only c. Explanation & Key Takeaways: • Optical fibre • When the light ray enters the optical fibre, it undergoes total internal reflection as the angle formed by the ray is greater than the critical angle. • Hence the only c is the correct option. • Total Internal reflection • Total internal reflection is a complete reflection of a ray of light within the same medium such as water or glass. • The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle • If the light is moving from a denser medium (water) to lighter medium(air) and the angle of incidence (i) is greater than the critical angle (c) that is i>c, then light undergoes the phenomenon called the total internal reflection. Important Notes: • Refraction of light • Bending of light away from normal while moving from one medium to another. • For example, a view of a broken pencil or coin inserted in a beaker of water. • Reflection of light • Incident ray gets reflected from the polished surface having the angle of incidence equal to the angle of reflection. • Dispersion of light • This process of white light splitting into its constituent colours is termed dispersion. • For example when light passes from prism then it splits into its spectrum of colours (in order violet, indigo, blue, green, yellow, orange, and red called VIBGYOR). Related Concepts: • Optical fibres are used in the communication devices to send and receive data. • Benefits of optical fibre cable • The data security is excellent. • It is cost-effective. • It won’t be affected by interference. • Less signal degradation. • Thin and non-flammable. • Economical and cost-effective. • Less power consumption. • Optical fibres are also used in endoscopy.