Optical fibers transmit light signals using the principle of total internal reflection. The light signals enter the fiber at an angle greater than the critical angle, which causes the light to be reflected entirely within the fiber. This continuous reflection ensures that the light travels through the fiber even if the fiber is bent. 
A hemispherical vessel is completely filled with a liquid of refractive index \( \mu \). A small coin is kept at the lowest point \( O \) of the vessel as shown in the figure. The minimum value of the refractive index of the liquid so that a person can see the coin from point \( E \) (at the level of the vessel) is:
A transparent block A having refractive index $ \mu_2 = 1.25 $ is surrounded by another medium of refractive index $ \mu_1 = 1.0 $ as shown in figure. A light ray is incident on the flat face of the block with incident angle $ \theta $ as shown in figure. What is the maximum value of $ \theta $ for which light suffers total internal reflection at the top surface of the block ?
“One of these days you’re going to talk yourself into a load of trouble,” her father said aggressively. What do you learn about Sophie’s father from these lines? (Going Places)
Write a letter to the editor of a local newspaper expressing your concerns about the increasing “Pollution levels in your city”. You are an environmentalist, Radha/Rakesh, 46, Peak Colony, Haranagar. You may use the following cues along with your own ideas: 