Question 1

The human eye forms the image of an object at its:

Accepted Answer

The human eye forms the image of an object at the retina. The light enters through the cornea and pupil, passes through the crystalline lens, and is focused on the light-sensitive screen called the retina.

Question 2

The least distance of distinct vision for a young adult with normal vision is about:

Accepted Answer

The least distance of distinct vision for a normal human eye is 25 cm. Below this distance, the eye cannot focus comfortably without strain.

Question 3

The change in focal length of an eye lens is caused by the action of the:

Accepted Answer

The change in focal length of the eye lens is caused by the action of the ciliary muscles. They alter the curvature and thickness of the flexible crystalline lens to focus objects at various distances.

Question 4

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

Accepted Answer

The power of the lens for distant vision is P = -5.5 D. Focal length f = 1/P = 1 / (-5.5 m^-1) = -100 / 5.5 cm = -18.18 cm.

Question 5

The dark muscular diaphragm that controls the size of the pupil is:

Accepted Answer

The iris is a dark muscular diaphragm that controls the size of the pupil. It regulates the amount of light entering the eye by adjusting the aperture size.

The Human Eye and Colourful World — CBSE Class 10 Science Important Questions & Revision Notes