In the spectrum obtained by the dispersion of white light through a prism,which color band is located in the middle?

$(a)$ How does refraction take place in the atmosphere? Why do stars twinkle but not the planets?
$(b)$ State any two effects of atmospheric refraction on the sun as observed from the Earth.

Explain the refraction of light through a triangular glass prism using a labelled ray diagram. Hence,define the angle of deviation.

Light coming from the sun is white light and contains seven colours.

How can you identify the type of vision defect a person is suffering from by physically touching their spectacles?

The colour of light which is deviated the least by a prism in the spectrum of white light is