Light of different colours propagates through air:

Two monochromatic (wavelength $\lambda = a/5$) and coherent sources of electromagnetic waves are placed on the $x$-axis at the points $(2a, 0)$ and $(-a, 0)$. $A$ detector moves in a circle of radius $R (R \gg 2a)$ whose center is at the origin. The number of maximas detected during one circular revolution by the detector are

Mention the colours which have the least and the most wavelength in visible light.

Red light differs from blue light in its

The difference in the number of waves when yellow light propagates through air and vacuum columns of the same thickness is $1$. The thickness of the air column is $....\,mm$. [Refractive index of air $= 1.0003$,wavelength of yellow light in vacuum $= 6000\,\mathring{A}$]

Fraunhofer lines are produced by the absorption of light in