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

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

Answer the following questions:
$(a)$ When a low flying aircraft passes overhead,we sometimes notice a slight shaking of the picture on our $TV$ screen. Suggest a possible explanation.
$(b)$ As you have learnt in the text,the principle of linear superposition of wave displacement is basic to understanding intensity distributions in diffraction and interference patterns. What is the justification of this principle?

Match Column-$1$ with Column-$2$ when a wave propagating in a denser medium enters a rarer medium:

Column-$1$	Column-$2$
$(a)$ Speed	$(i)$ Increases
$(b)$ Its amplitude	$(ii)$ Decreases
	$(iii)$ Remains constant

$A$ leaf which contains only green pigments is illuminated by a laser light of wavelength $0.6328 \,\mu m$. It would appear to be

Write the difference between the interference pattern and diffraction pattern.