# To Determine Radius of Curvature of a Given Spherical Surface by a Spherometer - Physics Practical Class 11 Viva Questions with Answers

1. What is a spherometer?
2. Answer. A spherometer is an instrument used to measure the radius of curvature of a curved surface or a sphere accurately.

3. Spherometer works on what principle?
4. Answer. The spherometer works on the principle of the micrometer screw.

5. Mention the least count of the spherometer.
6. Answer. The least count of the spherometer is 0.01mm.

7. Define the pitch of the spherometer.
8. Answer. pitch is described as the distance advanced by the central screw in one complete rotation of the circular disc scale.

9. What is the formula to calculate the least count of a spherometer?
10. Answer. The least count is given by the formula:

Least count = Pitch of the spherometer screw / Number of divisions on the circular scale

11. What is the value of the pitch of the screw?
12. Answer. The Pitch of the screw is 1 mm.

13. What is the formula to calculate the radius of curvature using a spherometer?
14. Answer. It is given by the formula:

$$\begin{array}{l}R=\frac{l^{2}}{6h}+\frac{h}{2}\end{array}$$

15. Choose YES or NO: Can the central leg of the spherometer move in downward and upward directions?
16. Answer. YES. The central leg can be moved both upwards and downwards.

17. What would be the distance moved by the screw in 10 complete rotations?
18. Answer. Distance moved by the screw in 10 complete rotations will be 10 mm

19. What will be the number of divisions on the circular scale?
20. Answer. The number of divisions on the circular scale will be 100.

21. Who invented the spherometer?
22. Answer. The spherometer was invented in 1810 by the French optician Robert-Aglae Cauchoix.

23. For what purpose do astronomers use the spherometer?
24. Answer. Astronomers used a spherometer for grinding lenses and curved mirrors.

25. Spherometer consists of how many outer legs?
26. Answer. The spherometer consists of three outer legs.