Question

1 AU is equal to
$\text{A}\text{. }1.5\times {10}^{11}m$
$\text{B}\text{. }1.5\times {10}^{10}m$
$\text{C}\text{. }1.5\times {10}^{9}m$
$\text{D}\text{. }1.5\times {10}^{-11}m$

Answer 1

Hint: 1 AU is called as one astronomical unit. Astronomical unit is a unit of length used to measure the distances in space. For example, the distance between stars situated very far. 1 Au is defined as the average distance between sun and earth.

Complete step by step answer:
The full form of AU is an astronomical unit. It is a unit of length. The distance between stars and planets is measured in the Astronomical Unit.
1 AU is defined as the average distance between the sun and the earth. From the data gathered through research, it has been found that the average distance between sun and our earth is approximately equal to a length of $1.5\times {10}^{11}$metres.
Therefore, the value of 1 AU is equal to $1.5\times {10}^{11}$metres.
Hence the correct option is A.
As you can see that the length of 1 astronomical unit is very large. Due to this reason we do not use this unit of length in our daily life. The unit AU is used by astronomers or the scientists involved in the research of space. The lengths or the distances that we common people deal with are in metres and kilometres and therefore we do not need the astronomical unit to measure lengths.
Additional Information: Other than AU, the units of length that are used to measure the distances in space are light years and parsec.
One light year is equal to the distance travelled by light in vacuum in one year.
One parsec is the distance which subtends a parallax angle of one arcsecond.

Note: The orbit in which our earth revolves around the sun is elliptical in shape with the sun at one of the foci of this ellipse. The distance between one focus of the ellipse and any point on the ellipse keeps changes. Therefore, the distance between sun and earth is not fixed.
That is why 1 AU is said to be the average distance between sun and earth.