Why pinning down waves spreads them

Science · Quantum & Modern Physics · ages 19-20

Name ______________________ Date ____________

A sharper microscope can beat the uncertainty limit.
Circle one: True False
What does the uncertainty relation say?
- Delta x times delta p is at least h-bar over two
- Delta x plus delta p equals h-bar
- Delta x times delta p is zero
Why does squeezing position widen momentum?
- Detectors heat the particle up
- More wavelengths enter, each with its own momentum
- Electrons repel the walls
An electron is squeezed from an atom into a nucleus. What happens to its momentum spread?
- It shrinks a lot
- It stays the same
- It grows a lot
A state living 1e-8 s has a frequency spread near 8000000 Hz. A state living twice as long has what spread in Hz?
Answer: ______________
Which pair carries the famous uncertainty limit?
- Charge and mass
- Position and momentum
- Speed and brightness
Delta x halves. The minimum delta p changes by what factor?
Answer: ______________
Uncertainty comes from the photon kick when we measure position.
Circle one: True False

Answer key

For grown-ups. Fold this page away before handing over the rest.

False · The limit sits in the quantum state, not the gear.
Delta x times delta p is at least h-bar over two · Position and momentum spreads share a minimum product.
More wavelengths enter, each with its own momentum · Localising needs many wavelengths, hence many momenta.
It grows a lot · Tighter boxes demand wider momentum spreads.
4000000 · Spread runs inverse to lifetime, so double life halves it.
Position and momentum · The wave-packet argument links position with momentum.
2 · Minimum product is fixed, so halving one doubles the other.
False · Kicks disturb, but the limit holds with no measurement at all.