Question

1. The speed of light in vacuum is ……….. 2. Power of a lens is the ………. of its focal length.
3. The SI unit of power is ………..
4. A ………. lens will always give a virtual, erect and diminished image, irrespective of the position of the object.
5. A positive sign in the value of magnification indicates that the image is ………. .
6. Focal length of lens, having power – 5D, will be ___________
7. Focal length of a convex lens is 2 m. The power of lens wil​

Answer 1

1. The speed of light in vacuum is 3×10⁸ m/s.

2. Power of a lens is the reciprocal of its focal length.

3. The SI unit of power is watt.

4. A concave lens will always give a virtual, erect and diminished image, irrespective of the position of the object.

5. A positive sign in the value of magnification indicates that the image is virtual.

6. Focal length of lens, having power – 5D, will be 20 cm.

7. Focal length of a convex lens is 2 m. The power of lens wil −0.5 dioptre.

Answer 2

The speed of light in vacuum is ……….. 2. Power of a lens is the ………. of its focal length.

3. The SI unit of power is ………..

4. A ………. lens will always give a virtual, erect and diminished image, irrespective of the position of the object.

5. A positive sign in the value of magnification indicates that the image is ………. .

6. Focal length of lens, having power – 5D, will be ___________

7. Focal length of a convex lens is 2 m. The power of lens wil