Classical Thinking

The arrangement of dispersion without deviation is used in,

In optical instruments to minimise the effect of dispersion and obtain clear and well-defined images,

A thin prism $P_1$ with refracting angle $4°$ and made from glass of refractive index $1.54$ is combined with another prism $P_2$ made from glass of refractive index $1.72\text{,}$ with vertex opposite to $P_1$ to produce dispersion without deviation. The angle of prism $P_2$ is,

The first explanation of rainbow was given by,

The complete circle of rainbow can be seen when,

To observe any rainbow the altitude of the sun or the angle made by the sun with the horizontal should be,

The primary rainbow is due to ________ total internal reflection inside droplet and two refractions.

Angular width of primary rainbow is,