according to the concept of length contraction, what happens to the length of an object as it approaches the…

Answer:

D. It is observed as contracting and then expanding back to its original length.

Explanation:

Step1: Recall length - contraction formula

The length contraction formula is $L = L_0\sqrt{1-\frac{v^{2}}{c^{2}}}$, where $L$ is the observed length, $L_0$ is the proper length (length at rest), $v$ is the relative velocity of the object, and $c$ is the speed of light.

Step2: Analyze when approaching speed of light

As the object approaches the speed of light ($v\rightarrow c$), $\frac{v^{2}}{c^{2}}\rightarrow1$, and $\sqrt{1 - \frac{v^{2}}{c^{2}}}\rightarrow0$, so $L\rightarrow0$, i.e., the object is observed to contract.

Step3: Analyze when slowing down

As the object slows down ($v\rightarrow0$), $\frac{v^{2}}{c^{2}}\rightarrow0$, and $\sqrt{1-\frac{v^{2}}{c^{2}}}\rightarrow1$, so $L\rightarrow L_0$. The object expands back to its original length.