To Determine Radius of Curvature of a Given Spherical Surface by a Spherometer Viva Questions with Answers

Spherometers are the measuring devices used to determine the radius of curvature of curved surfaces with precision.

• Originally, opticians used these tools to measure the curvature of the surface of a lens.
• A spherometer comprises a solid metal or plastic base with three equally spaced legs or arms.
• The working principle of a spherometer is based on the micrometer screw. 
• It is used to measure the radius of curvature of a spherical surface with a small thickness of flat materials such as glass.
• A spherometer consists of a base circle with three outer legs, also known as the radius of the base circle, and a ring with the radius of the base circle known.
• The spherometer's outer legs may be modified according to the inner holes.
• The central leg may be adjusted both upward and downward.
• The reading device on the central leg should be moved to take the measurements.

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Ques. Define the radius of curvature.

Ans. The radius of curvature of the spherical mirror is the radius of the hollow sphere of which it is a part. In other terms, the radius of curvature of a spherical mirror is the distance between its pole and center of curvature.

Ques. What is a spherical surface?

Ans. A surface that is a part of a sphere is said to be a spherical surface. It can curve inward or outward depending on whether it is concave or convex. Several fields, including optics, engineering, and architecture, make use of spherical surfaces.

Ques. What is a spherometer?

Ans. A spherometer is a device used to precisely measure the radius of curvature of a curved surface. Originally, opticians used these tools to measure the curvature of the surface of a lens.

Ques. What is the working principle of a spherometer?

Ans. The working principle of a spherometer is based on the micrometer screw. It is used to measure the radius of curvature of a spherical surface with a small thickness of flat materials such as glass.

Ques. Who invented the spherometer?

Ans. In 1810, French optician Robert-Aglae Cauchoix developed the first known spherometer. Beginning in the nineteenth century, they were created largely for use by opticians in grinding lenses and astronomers in grinding lenses and curved mirrors.

Ques. What are the different parts of a spherometer?

Ans. A spherometer usually consists of up of a base circular with three outside legs, one center leg, and a reading device.

Ques. Why does a spherometer have three legs?

Ans. A spherometer consists of three legs that form an equilateral triangle. The spherometer's three legs are used to measure both positively and negatively curved surfaces.

Ques. Define the pitch of the spherometer.

Ans. The pitch of a circular disc scale of a spherometer is defined as the distance advanced by the center screw in one complete rotation.

Ques. For what purpose do astronomers use the spherometer?

Ans. In the field of astronomy, spherometers have been used for grinding lenses and curved mirrors.

Ques. What is the formula to calculate the radius of curvature using a spherometer?

Ans. The radius of curvature measured by a spherometer is given by

\(R = \frac{l^2}{6h} + \frac{h}{2}\)

Ques. What is the formula to calculate the least count of a spherometer?

Ans. The least count of the spherometer is given by

Least Count = (Pitch of the spherometer screw)/(Number of circular divisions)

Ques. Mention the least count of the spherometer.

Ans. The least count of the spherometer is 0.01 mm.

Ques. What is the value of the pitch of the screw?

Ans. The distance covered by the circular disc in one complete rotation along the main scale is known as the pitch. Therefore the pitch of a spherometer is 1 mm = 0.1 cm.

Ques. What will be the number of divisions on the circular scale?

Ans. This circular scale will have a total of 100 divisions on it.

Ques. Can the central leg of the spherometer move in downward and upward directions?

Ans. The spherometer's outside legs may be adjusted with respect to the inner holes. This is done to make room for smaller surfaces. The central leg may be adjusted both upward and downward. The reading device on the center leg should be moved to take the measurements.

Ques. What would be the distance moved by the screw in 10 complete rotations?

Ans. On the linear scale, the screw moves 10 mm in 10 complete rotations.

Ques. How many legs does a spherometer have?

Ans. A spherometer is composed of a base circle with three outside legs, also known as the radius of the base circle, and a ring with the radius of the base circle known. The spherometer's outside legs may be adjusted according to the inner holes.

Ques. What is zero error in a spherometer?

Ans. The reading on the plane glass sheet is the zero error in a spherometer.

Ques. How to find the zero error in a spherometer?

Ans. A spherometer does not have a zero error since the result is produced by subtracting the final and initial readings.

Ques. How can the accuracy of the spherometer increase? 

Ans. The Spherometer's accuracy is determined by the magnitude of the least count. If the least count is small, the probability of accuracy increases. The accuracy level may be modified by adjusting the divisions of the circular scale.

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