MEDIUM
12th West Bengal Board
IMPORTANT
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A normal eye is not able to see objects closer than 25 cm because :

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Important Questions on Human Eye and Optical Instruments

HARD
12th West Bengal Board
IMPORTANT
If F be the focal length of a camera lens and D the diameter of its aperture, then the f-number of the lens is
MEDIUM
12th West Bengal Board
IMPORTANT

Magnifying power of an astronomical telescope normal vision is

MEDIUM
12th West Bengal Board
IMPORTANT
If focal length of the eyepiece of a telescope is doubled its magnifying power m will be
HARD
12th West Bengal Board
IMPORTANT
The least distance of distinct vision of a person is 75 cm The focal length of the reading spectacles for such a person should be
MEDIUM
12th West Bengal Board
IMPORTANT
in a compound microscope, the intermediate image is
HARD
12th West Bengal Board
IMPORTANT

A man with normal vision uses a magnifying lens of focal length 10 cm. Then

MEDIUM
12th West Bengal Board
IMPORTANT

Write W for the incorrect statements and R for the correct ones:

The cones of human eye respond to strong light and cause sensation of colour and colour difference while the rods are sensitive to feeble light and movement of objects.

MEDIUM
12th West Bengal Board
IMPORTANT

Write W for the incorrect statements and R for the correct ones:

Concave lenses are used to remedy long-sight defect and convex lens for short- sight defect.