Spherometer: Measuring Curved Surfaces in Physics
by Yuvi K - December 16, 2023
Introduction to Spherometer
A spherometer is a device used to measure the curvature of curved surfaces. It is an instrument used in the field of physics that is used to measure the degree of curvature or radius of a given surface. The purpose of this instrument is to measure the curvature of a surface or object for research and other applications. This instrument can also be used to measure a surface’s radius, as well as its radius of curvature.
What is a Spherometer?
A spherometer is an instrument used to measure the radius of curvature of any curved surface. The term spherometer is derived from two Greek words “sphaira” which means sphere and “metron” which means measure. It is a lightweight measuring device, shaped like a disc with a measurement scale attached to it. The device consists of three legs which are adjustable and the small central platform is connected to the legs. A micrometer screw is used to turn the central platform and by controlling the radial movement, the exact radius or curvature of the curved surface can be determined.
Principle and Working of Spherometer
The principle of measurement with a spherometer is based on the principle of triangulation. This is because, with a spherometer, three points are marked on a curved surface. This marks three vertices of a triangle which are then connected by three equal arms. This triangle can be constructed as a perfect equilateral triangle with a known length of sides. Upon knowing the three length measurements, the radius of curvature of the surface can be calculated.
When a spherometer is used to measure the curvature of a curved surface, the central platform is placed on the curved surface, with the legs set at a level position. The micrometer screw on the central platform is then turned, altering the radius of the central platform. This, in turn, alters the length of the three legs of the spherometer at the same time.
Using the micrometer screw and the measurement scale, the length of the three legs is fractionally adjusted until a flat equilateral triangle is formed. Once the perfect triangle is formed, the curved surface is exactly of the right radius or curvature. The length of each side is then measured and the radius is calculated.
Types of Spherometer
1. Fixed Spherometer
A fixed spherometer is a type of spherometer where the radius of the main platform remains constant. The three adjustable legs are arranged such that each leg measures the same distance from the centre of the platform. The length of each leg can be adjusted using the screws that are connected to them.
2. Variable Spherometer
The variable spherometer is the most widely used type of spherometer and it is also known as the double-arm spherometer. In this type of spherometer, the radius of the main platform is adjustable, meaning that the length of the three legs can be adjusted as per the curvature of the object surface.
Advantages of Spherometer
- Spherometer is a very efficient instrument, as it allows for accurate measurement of the radius of a curved surface.
- It is a cost-effective tool and it is easy to use.
- It is a lightweight device, so it can be easily carried and used in remote areas.
- Due to its adjustable legs, it can be used to measure surfaces of varying curvatures.
Drawbacks of Spherometer
- As the device comprises of three adjustable legs, it is difficult to use it in narrow or tight spaces.
- The device is not suitable for measuring small and fine surfaces, as it is designed for large surfaces.
Conclusion
The spherometer is an instrument that is used to measure the radius of curvature of any curved surface. It is a lightweight device which allows for accurate measuring of curved surfaces with great ease. It is a device that is widely used in physics and engineering and it has become an important tool in the field of measuring curved surfaces.
