How many surfaces bound a prism? How many refractions does a beam of white light suffer, when it is passed through a prism?

Water in deep sea is blue in colour. Why?

The electronic configuration of an element is 2, 8, 4. State its:

1. Group and period in the modern periodic table.
2. Name and write its one physical property.

Write the function of the retina in the human eye.

How does the thickness of the eye lens change when we shift looking from a distant tree to reading a book?

Why does the Sun appear reddish early in the morning?

Explain why, when the sun is overhead at noon, it appears white, but when the same sun is near the horizon at sunset, it appears red?

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?

A star sometimes appears brighter and some other times fainter. What is this effect called? State the reason for this effect.

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?