Question

7.
उत्तल लेंस की सहायता से एक उत्तल दर्पण की फोकस दूरी ज्ञात करें।
Find the focal length of a convex mirror using a convex lens
चल सूक्ष्मदर्शी की सहायता से काँच की सिल्ली का अपवर्तनांक ज्ञात करें।
Determine refractive index of glass slab using travelling microscope
8.​

Answer 1

Answer:

उत्तल लेंस की सहायता से एक उत्तल दर्पण की फोकस दूरी ज्ञात करें।

Explanation:

उत्तल लेंस की सहायता से एक उत्तल दर्पण की फोकस दूरी ज्ञात करें।

Answer 2

As a convex mirror always forms a virtual image, its focal length cannot be found directly as for a concave mirror.

Explanation:

For this purpose, the indirect method is used, as described below.

• An auxiliary convex lens L is introduced between the convex mirror M and object needle O as shown in ray diagram (a).
• Keeping the object needle at distance about 1.5 times rough focal length of convex lens, the position of convex mirror behind convex lens is so adjusted that a real and inverted image of object needle O, is formed at O itself.
• Under such condition, the light rays are incident normally over the convex mirror to retrace their path. In the absence of convex mirror, these rays would have met at centre of curvature C of the convex mirror.
• The distance PC gives the radius of curvature R of the mirror.