Spherometer viva

 Q.1 What is the object of your experiment ?

Ans: Determination of the radius of curvature of given spherical (convex) mirror using spherometer and to calculate its focal length.

Q.2 Why is it called a spherometer ?

Ans: Because it is used to measure the radius of curvature of spherical surfaces.

Q.3 For what other purpose the spherometer can be used besides measuring radius of curvature ?

Ans: It can also be used for the measurement of thickness of thin plates and small lengths.

Q.4 What is meant by pitch and least count of spherometer ?

Ans: 

Pitch of spherometer

It is the distance on the main scale for a complete rotation of the circular scale.

Least Count of spherometer

It is the smallest quantity that the instrument can measure exactly. 

Q.5 What is the pitch and least count of spherometer you are using ?

Ans: The pitch of spherometer is 0.1 cm and least count of spherometer is 0.001 cm ( or say what it actually is).

Q.6 What is the range of your spherometer ?

Ans: The range of spherometer is 10 mm on either side (or say what it actually is).

Q.7 What is the degree of accuracy of spherometer ?

Ans: The degree of accuracy of spherometer is one-hundredth of a millimetre.

Q.8 Is there zero error in spherometer and how we remove the error of spherometer ?

Ans: There is zero error in spherometer and reading on base plate is actually its zero error.

Q.9 Why is the main scale of spherometer marked on both sides ?

Ans: The main scale of spherometer is marked on both sides to measure the height and depth of the spherical surfaces.

Q.10 What is back-lash error of spherometer and how back-lash error to be avoided ?

Ans: This error is due to looseness in fitting between the screw and the nut.Due to this error, equal amount of rotation of the screw in opposite direction does not produce equal amount of linear motion of the screw. This error can be avoided if the screw is turned always in the same direction while taking an observation.

Q.11 Why the distance "l" between legs of the spherometer should be measured carefully ?

Ans: Because, the accuracy of the result mainly depends upon the square of "l". 

Q.12 Name the precision instruments used to measure length.

Ans: Vernier Callipers, Micrometer Screw Gauge, Spherometer

Q.13 Which of the two instruments is more accurate (1) micrometer screw gauge (2) Spherometer ?

Ans: Both the instruments have the equal degree of accuracy as both can measure up to one-hundredth of a millimetre.

Q.14 What is radius of curvature ?

Ans: It is the radius of the sphere of which the surface of a mirror is a part.

Q.15 What is the radius of curvature of a plane mirror ?

Ans: The radius of curvature of a plane mirror is infinite.

Q.16 Define Focal length || What is Focal Length ?

Ans: The distance between the pole and the principle focus of spherical mirror is called the focal lenght. The focal length of spherical mirror is half of its radius of curvature.