The focal length of a normal eye-lens is about

Important Questions on Human Eye and Optical Instruments

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 16 - Human Eye and Optical Instruments>EXERCISE 16>Q 3

An eye-specialist prescribes spectacles having combination of convex lens of focal length $40 \mathrm{cm}$  in contact with a concave lens of focal length $25 \mathrm{cm}.$ The power of this lens combination in dioptre is

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 16 - Human Eye and Optical Instruments>EXERCISE 16>Q 4

An object is placed at a distance $u$ from a simple microscope of focal length $f$. The angular magnification produced by the microscope depends

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 16 - Human Eye and Optical Instruments>EXERCISE 16>Q 5

A man looks at a tree of height $15 \mathrm{m}$ with a telescope of magnifying power $10$. To him, the tree appears

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 16 - Human Eye and Optical Instruments>EXERCISE 16>Q 6

To increase the magnifying power of a simple microscope,

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 16 - Human Eye and Optical Instruments>EXERCISE 16>Q 7

The magnifying power of an astronomical telescope is $15$. If the focal length of the object is $90 \mathrm{cm},$ then the focal length of the eyepiece is :

MEDIUM

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 16 - Human Eye and Optical Instruments>EXERCISE 16>Q 8

In which optical instrument, the final image is erect ?

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 16 - Human Eye and Optical Instruments>EXERCISE 16>Q 9

In which optical instrument, the eyepiece is a concave lens?

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 16 - Human Eye and Optical Instruments>EXERCISE 16>Q 10

The focal length of the objective of a compound microscope is $f_0$ and its distance from the eye-piece is $L.$ The object is at a distance $u$ from the objective. For proper functioning of the instrument it is necessary that