Explain the nature of image formed by human eye lens.

Why do stars seem higher than they actually are? Illustrate your answer with the help of a diagram.

Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

A person needs a lens of power, -5.5 dioptres for correcting his distant vision. For correcting his near vision, he needs a lens of power, +1.5 dioptres. What is the focal length of the lens required for correcting

1. Distant vision, and
2. Near vision?

Which is refracted most by a prism: red light or violet light? Explain why?

An object is moved closer to an eye. What changes must take place in the eye in order to keep the image in sharp focus?

Why does the sky appear dark instead of blue to an astronaut?

How many colours are there in a full spectrum of white light? Write the various colours of spectrum in the order, starting with red.

A narrow beam of light produces a spectrum XY on passing through a triangular glass prism.

1. State the colour at X and Y.
2. Why do the different components of white light bend through different angles with respect to the incident beam of light?

A person can comfortably read a book but finds it difficult to read the number on a bus parked 5 m away from him. Name the type of defect of vision he is suffering
from. Which type of lens should be used in his spectacles to correct his vision?