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Units and Measurement

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Physics Part I

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Physics

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
The photograph of a house occupies an area of 1.75 cm2on a 35 mm slide. The slide is projected on to a screen, and the area of the house on the screen is 1.55 m2. What is the linear magnification of the projector-screen arrangement.

Area space of space the space house space on space the space slide space equals space 1.75 space cm squared space

Area space of space the space image space of space the space house
space formed space on space the space screen space equals space 1.55 space straight m squared space equals space 1.55 cross times 10 to the power of 4 space cm squared space

Therefore comma space

Arial space magnification comma space straight m subscript straight a space equals space fraction numerator Area space of space image over denominator Area space of space object end fraction space

space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space fraction numerator 1.55 over denominator 1.75 end fraction cross times space 10 to the power of 4 space

So comma space linear space magnification comma space straight m subscript straight l space equals square root of straight m subscript straight a end root space

equals space square root of fraction numerator 1.55 over denominator 1.75 end fraction cross times space 10 to the power of 4 space end root space equals space 94.11 space
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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. 
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Give four examples of physical quantities.

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

Define unit.

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

Example: Unit of time is second. 

1172 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.


878 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