WAEC 2016 Physics · Question 1
Let x be the uncertainty in the measurements of position and p the uncertainty in measurement of momentum. The…
Question
Let x be the uncertainty in the measurements of position and p the uncertainty in measurement of momentum. The uncertainty principle relation is given as
- A.x . p = h
- B.x . p = h
- C.x . p = h
- D.x . p > h
Answer: C. x . p = h
Explanation written with AI and checked against the answer key
Analyze the question: The question asks for the correct mathematical statement of Heisenberg's Uncertainty Principle, relating the uncertainty in position (Δx) and the uncertainty in momentum (Δp).
Concept: Heisenberg's Uncertainty Principle says we cannot measure both the exact position and the exact momentum of a particle at the same time. The more precisely one is known, the less precisely the other can be known. The product of the two uncertainties therefore has a minimum value:
Δx · Δp ≥ ħ/2, where ħ = h/2π
In many WASSCE and school textbooks, this is written in the simpler order-of-magnitude form:
Δx · Δp ≥ h
Working through the options:
- A (Δx·Δp = h): Wrong. The principle sets a lower limit, not an exact value.
- B (Δx·Δp ≤ h): Wrong. This would put an upper limit on the product, and the principle says the opposite.
- C (Δx·Δp ≥ h): Correct. The product can never be smaller than a minimum value of the order of h. This is the "greater than or equal to" form.
- D (Δx·Δp > h): This is close, but it excludes the equality case. The principle allows the product to reach the minimum value, so "≥" is the better statement.
Answer: Option C.
Exam tip: Remember that the uncertainty principle sets a minimum on the product of uncertainties. Both quantities cannot be made arbitrarily small together, so the sign is always "≥" and never "≤".
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