A new unit ( … ) of length is chosen such…

Single correct+4 / -1Answer matches NTA’s final key

A new unit ( $\alpha$ ) of length is chosen such that it is equal to the speed of light in vacuum. What is the distance between Venus and Earth in terms of $\alpha$ units if light takes 6 min. 40 s to cover this distance?

$200\,\alpha$
$400\,\alpha$
$300\,\alpha$
$500\,\alpha$

Solution

The unit $\alpha$ is the distance light covers in one second (numerically $c$ metres). The light travel time is $6 \times 60 + 40 = 400$ s, so the distance is $400$ such units.

Answer: $400\,\alpha$ .

Answer checked against the official answer key. The solution is our own working.

JEE MAIN 2026 · Units and Measurements

Solution

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