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JEE Main levelOne or more correct optionsDifficulty 2 of 3as132

Which of the following are consistent with Heisenberg's uncertainty principle $Δ x Δ p \geq h /4 π$ ?

AAn electron cannot have simultaneously exactly known position and exactly known momentum.
BThe limit arises from poor design of present-day instruments and can be removed in principle.
CFor a very massive body the uncertainty in velocity is negligible for any practical $Δ x$ .
DIf $Δ x$ is halved, the minimum possible $Δ p$ doubles.

Answer: A, C, D

The relation is a fundamental limit (A true, B false). For large

m

,

Δ v = Δ p / m

is tiny (C true). Minimum

Δ p = h / (4 π Δ x)

is inversely proportional to

Δ x

(D true).

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