To confine an electron within a box of radius 10⁻¹⁴ m, what would its speed need to be?
Correct answer D. Greater than the speed of light
Explanation
By the uncertainty principle, confinement to 10⁻¹⁴ m gives a momentum uncertainty so large that a non-relativistic estimate of speed exceeds the speed of light, so electrons cannot exist in a nucleus.
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