In which direction is a rainbow formed during the morning hours in the rainy season?

$A$ person needs a lens of power $-4.5\, D$ for the correction of her vision.
$(a)$ What kind of defect in vision is she suffering from?
$(b)$ What is the focal length of the corrective lens?
$(c)$ What is the nature of the corrective lens?

Every colour travels with the same speed in a transparent medium.

Mention the factor on which scattering of light depends. Why does the sky appear dark in space?

What is the phenomenon of splitting of white light into its seven constituent colors called?

Why does it take some time to see objects in a cinema hall when we just enter the hall from bright sunlight? Explain in brief.