Explain clearly why, a person who has lost the sight of one eye is at a disadvantage compared with the normal person who has two good eyes.

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

How could you show that the colours of the spectrum combine to give white light?

A beam of light consisting of consists of three. namely red (R), Green (G) and yellow (Y) on the prism as shown below. Complete the diagram to show refracted and emergent ray.

A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

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?

Define the term power of accommodation. Write the modification in the curvature of the eye lens which enables us to see the nearby objects clearly?

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 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?

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

Five persons A, B, C, D and E have diabetes, leukaemia, asthma, meningitis and hepatitis, respectively.

1. Which of these persons can donate eyes?
2. Which of these persons cannot donate eyes?