CBSE 2022 · Region 3 · Set 1 · Q12 · 5 marks

A compound microscope consists of two converging lenses. One of them, of smaller aperture and smaller focal length is called objective and the other of slightly larger aperture and slightly larger focal length is called eye-piece. Both the lenses are fitted in a tube with an arrangement to vary the distance between them. A tiny object is placed in front of the objective at a distance slightly greater than its focal length. The objective produces the image of the object which acts as an object for the eye-piece. The eye piece, in turn produces the final magnified image.I. In a compound microscope the images formed by the objective and the eye-piece are respectively

(A)

virtual, real

(B)

real, virtual

(C)

virtual, virtual

(D)

real, real II. The magnification due to a compound microscope does not depend upon

(A)

the aperture of the objective and the eye-piece

(B)

the focal length of the objective and the eye-piece

(C)

the length of the tube

(D)

the colour of the light used III. Which of the following is not correct in the context of a compound microscope ?

(A)

Both the lenses are of short focal lengths.

(B)

The magnifying power increases by decreasing the focal lengths of the two lenses.

(C)

The distance between the two lenses is more than (fo + fe).

(D)

The microscope can be used as a telescope by interchanging the two lenses. IV. A compound microscope consists of an objective of 10X and an eye-piece of $\displaystyle 20$ X . The magnification due to the microscope would be

(A)

$\displaystyle 2$ (B) $\displaystyle 10$

(C)

$\displaystyle 30$

(D)

$\displaystyle 200$ V. The focal lengths of objective and eye-piece of a compound microscope are $\displaystyle 1.2$ cm and $\displaystyle 3.0$ cm respectively. The object is placed at a distance of $\displaystyle 1.25$ cm from the objective. If the final image is formed at infinity, the magnifying power of the microscope would be

(A)

$\displaystyle 100$

(B)

$\displaystyle 150$

(C)

$\displaystyle 200$

(D)

$\displaystyle 250$

CBSE Class 12 Physics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.