# Which among the following is not a unit of time 1. Parsec 2. Second 3. Light Year 4. Year

27 views
in Physics
closed

Which among the following is not a unit of time

1. Parsec

2. Second

3. Light Year

4. Year

1. Only 2
2. Both 1 and 3
3. 2, 3 and 4
4. 1, 2 and 4

by (54.5k points)
selected

Correct Answer - Option 2 : Both 1 and 3

CONCEPT:

Parsec (parallactic second):

• It is the largest practical unit of distance used in astronomy.
• It is defined as the distance at which an arc of the length of 1 astronomical unit subtends an angle of 1 second of arc.

1 parsec = 3.08 × 1016 m

Light year:

• It is the distance travelled by light in a vacuum in one year.
• light-year is used in astronomy to measure the distances of nearby stars.

1 light-year = 1ly = 9.467 × 1015 m

• Parsec: It is a unit of length used to measure the large distances to astronomical objects outside the solar system
• Second: It is the standard international (SI) unit of time
• Year: It is also a unit of time

1 year = 365 days

1 day = 48 hours

1 hours = 3600 seconds

EXPLAINATION:

• From the above discussion, it is clear that Parsec and Light year are not units of time. Hence, option (2) is correct.