what is the order of magnitude of a physical quantity ?
Order of magnitude:
The order of magnitude tells us about the largeness or smallness of a physical quantity. To find the order of magnitude the value of the physical quantity is expressed as a × 10bwhere 1 ≤ a < 10 and b is a positive or a negative integer. The exponent of 10, here it is b, is called of the order of magnitude. To compare the physical quantities we must express them in proper units.
Example: Length of a football is 91 m, which can be expressed as 9.1 × 101 m. Length of a housefly is 5 × 10-3 m. So, the order of magnitude of football field is 1 and that of the house fly is -3. The difference is 1 - (-3) = 4. Thus, we can say the length of a football field is 4 orders of magnitude larger than the length of a housefly.