What color of light is produced when blue and yellow light are superimposed?

$A$ person suffering from an eye defect uses lenses of power $-1\, D$. Name the defect he is suffering from and the nature of lens used.

Which phenomenon is responsible for the reddish appearance of the Sun at sunrise and sunset?

What is Presbyopia?

How does an eye manage to see objects in dim light and bright light?

Draw a ray diagram showing the dispersion through a prism when a narrow beam of white light is incident on one of its refracting surfaces. Also,indicate the order of the colours of the spectrum obtained.