Soraya wants a complete report on one electron at one moment: exactly where it is, and exactly its momentum. Quantum physics has a limit waiting for her.
Momentum is mass times velocity; you met it in the momentum topic. This lesson states one more fact about quantum objects: a limit on what can be known about them.
Certain pairs of properties of a quantum object cannot both be known exactly at the same time.
Position and momentum are the famous pair. The more exactly an electron's position is known, the less exactly its momentum can be known.
The trade runs both ways. A sharp momentum measurement leaves the position less certain.
It is a statement about pairs. Position pairs with momentum. Knowing an electron's mass or its charge exactly costs nothing: those are not part of such a pair.
This course states the limit in words only, with no equation. What the limit rules out is one thing: a quantum object whose position and momentum are both exactly known at the same moment.
The limit is part of why quantum objects get pale bands in our drawings: a band of possible positions, a band of possible momentum values, and no way to make both bands narrow at once.
A measurement pins an electron's position down very precisely. What does the Heisenberg uncertainty principle say happens to what can be known about its momentum?
Position and momentum are one of the principle's pairs.
The more exactly the position is known, the less exactly the momentum can be known at the same time.
The sharp position measurement therefore leaves the electron's momentum less certain.
Its momentum becomes less certain.
Kenji reports an electron's mass and its charge, both known very exactly. Does the Heisenberg uncertainty principle forbid his report?
The principle limits certain pairs of properties, such as position and momentum.
Mass and charge are fixed properties of the electron, not one of those pairs.
So both can be known exactly at the same time.
No. The principle limits pairs like position and momentum, and mass with charge is not such a pair.
Which pair of an electron's properties cannot both be known exactly at the same time?
Jocasta measures an electron's position very precisely. According to the Heisenberg uncertainty principle, what happens to what can be known about the electron's momentum at that moment?
Kenji says: 'The Heisenberg uncertainty principle applies to certain pairs of properties, not to every pair.' Is Kenji correct?
Which statement is the Heisenberg uncertainty principle?
A measurement leaves a proton's momentum almost exactly known. What does the Heisenberg uncertainty principle say about the proton's position at that moment?
Which situation shows the Heisenberg uncertainty principle at work?