What is meant by the spectrum of white light?

The figure below shows the refraction of a ray through a prism. Copy the diagram and,ignoring dispersion at the faces $AB$ and $AC$,mark the following angles: $(i)$ The angle of incidence,$(ii)$ the angle of refraction at the face $AB$,$(iii)$ the angle of emergence,and $(iv)$ the angle of deviation.

What is another name for the defect of myopia?

Draw ray diagrams each showing $(i)$ myopic eye and $(ii)$ hypermetropic eye.

$(a)$ What will be the colour of the sky in the absence of an atmosphere?
$(b)$ Why are traffic light signals (or danger signals) of red colour?

Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?