How to determine the uncertainty of positon?

[Sophie Zhou 2H]

Hi, I was confused by which value we should use in the Heisenberg equation. Because I originally thought that for the uncertainty we either have something like the diameter of an atom or the value after the +- sign that represents uncertainty. For example, a ball has a diameter of 30cm +- 5cm. We use 5cm as the uncertainty for this equation. But on a reviewing session, the TA told us that we should use the number that is equal to upper bound minus lower bound, which in this case the uncertainty of position becomes 10cm (5cm larger or 5cm smaller). So I was absolutely confused. Thanks for answering this question.

[Danika Suh 2L]

Hi! In regards to the Heisenberg equation, the uncertainty of position covers the entire range of possible values. From this, in your example, the range would be 5 values below and above 30cm, otherwise stated as a range of 10cm. You would use the value of 10cm, instead of 5cm, as it covers the full spread of possible values for the uncertainty of position. Hope this helps!