Let $\vec a$ be a non-zero vector of magnitude 'a' and $λ$ is a non-zero scalar, then $λ\vec a$ is a unit vector if

$a=\frac{1}{|λ|}$

The correct answer is Option (2) → $a=\frac{1}{|λ|}$

Given:

$|\vec{a}| = a$, and $\lambda$ is a scalar.

For $\lambda \vec{a}$ to be a unit vector, its magnitude must be 1:

$|\lambda \vec{a}| = 1$

$|\lambda| \, |\vec{a}| = 1$

$|\lambda| \, a = 1$

$|\lambda| = \frac{1}{a}$

Therefore, $\lambda a⃗$ is a unit vector if $|\lambda| = \frac{1}{a}$.