The longest and the shortest wavelengths (in $\mu m$) for red and violet light are respectively:

Which of the following is not a secondary color?

$(a)$ Demonstrate an activity with a well-labelled diagram to prove that white light is made up of seven colours.
$(b)$ Which colour of light bends least and which one the most while passing out from the prism? Also,state the reason for the same.

$A$ beam of white light falling on a glass prism gets split up into seven colours marked $1$ to $7$ as shown in the diagram.
$(a)$ The colours at positions marked $3$ and $5$ are similar to the colour of the sky and the colour of gold metal respectively. Is the above statement made by the student correct or incorrect? Justify.
$(b)$ Which of the above shown positions corresponds approximately to the colour of:
$(i)$ a brinjal
$(ii)$ danger signal
$(iii)$ neel (indigo) which is applied to clothes
$(iv)$ orange

Which of the following phenomena of light are involved in the formation of a rainbow?

$(a)$ What is dispersion of white light? What is the cause of such dispersion? Draw a diagram to show the dispersion of white light by a glass prism.
$(b)$ $A$ glass prism is able to produce a spectrum when white light passes through it,but a glass slab does not produce any spectrum. Explain why this is so.