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Class 10 Class 12
A student measures the thickness of a human hair by looking at it through a microscope of magnification 100. He makes 20 observations and finds that the average width of the hair in the field of view of the microscope is 3.5 mm. What is the estimate on the thickness of hair ?

Magnification of the microscope = 100

Average width of hair in the field of view of the microscope = 3.5 mm

Therefore, actual thinckness of the hair =

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What is the need of measurement?

To get the complete knowledge of any physical quantity, measurement is needed. Measurement of any physical quantity involves comparison with a certain basic, arbitrarily chosen, internationally accepted reference standard called unit. Knowledge without measurement is incomplete and unsatisfactory.
825 Views

Define unit.

The quantity used as a standard of measurement is called unit.

Example: Unit of time is second.

1172 Views

What is measurement?

Measurement is the process of attaching a numeric value to an aspect of a natural phenomenon. Measurement is making the quantitative knowledge of a physical quantity.
1289 Views

Give four examples of physical quantities.

Examples of Physical quantitie are force, mass, density and power.
821 Views

Define physical quantity.

A measurable quantity in terms of which laws of Physics can be expressed is called physical quantity.

The result of a measurement of a physical quantity is expressed by a number accompanied by a unit.

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