Exercise

A tank is filled with water to a height of $12.5 \mathrm{c}\mathrm{m}$. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be $9.4 \mathrm{c}\mathrm{m}$. What is the refractive index of water? If water is replaced by a liquid of refractive index $1.63$ up to the same height, by what distance would the microscope have to be moved to focus on the needle again?

The ratio between the speed of light in medium to speed in vacuum is the refractive index. When light travels in a medium other than the vacuum, the atoms of that medium continually absorb and re-emit the particles of light, slowing down the speed of light. 

The refractive index of glass is $1.5$. The critical angle of the glass is,

Why must both the objective and the eyepiece of a compound microscope have short focal lengths?

Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?

An object is placed at $20 \mathrm{cm}$ from a concave mirror of focal length $20 \mathrm{cm},$ its image will be formed at-

A virtual and magnified image can be obtained by-

What you mean by total internal reflection? Draw a diagram indicating the total internal reflection. State the necessary conditions for total internal reflection to take place. Describe the formation of mirage based on total internal reflection with the help of a diagram.