Question

Which of the following is not a unit of length?

• A. micron
• B. light year
• C. angstrom
• D. radian

Answer 1

The correct option is D

radian

Explanation of correct option:

In the case of option (D),

Radian is a unit of plane angular measure.

Explanation of incorrect options:

In the case of option (A), $1micron={10}^{-6}m$

In the case of option (B), $1lightyear=9.4\times {10}^{15}m$

In the case of option (C), $1angstrom={10}^{-10}m$

Hence, option (D) is the correct answer.