Question

Parsec is the unit of which physical quantity
A) Time
B) Distance
C) Frequency
D) Angular acceleration

Answer 1

Hint: We measure physical quantities with their standard units. For space objects light-year is used to describe their distance. The distance that light travels in one Earth year is called a light year. Parsec is also a unit for measurement which is used for measurements outside the solar system.

Complete answer:
Parsec or parallactic second or is a unit of distance. It is defined as the distance at which one AU (astronomical unit) subtends an angle of one arc second, and is equal to 3.26 light years. Or, it is the unit of length which is used to measure the large distances of celestial bodies outside the solar system. It is obtained by using trigonometry and parallax. One parsec is equal to the length of an adjacent side of the imaginary right triangle in space. The two dimensions on which this triangle is based are the opposite side (defined as 1 AU-distance from the Earth to the Sun) and the angle (defined as 1 arc second). Using these two measurements, along trigonometry, the length of the adjacent side (the parsec) can be determined.

Therefore, the correct option is option B.

Note:
The Astronomical unit is useful for measuring distances within the Solar System. But the Solar System is tiny compared to the size of the universe and much bigger units are needed when we go beyond it. Hence, light year and parsec is used. A light year is defined as the distance covered by a beam of light in one year. But, parsec can be used for measuring larger distances and it is the largest unit used for measurement.