Question

The uncertainty principle arises from a common-sense idea: To measure something, you must affect it somehow. For instance, when you use a pressure gauge to measure air pressure in a car tire you release a small amount of air into the gauge.

• When you shine a light on an object, the momentum from the photons that make up that light impacts the object. For macroscopic objects, this will have no measurable effect. Describe why this is different for atomic-sized objects.
• Suppose you shine a very long wavelength light on one electron and a very short wavelength light on another electron. What differences will you observe?
• Why does shining very short wavelength photons on an electron not tell you exactly where the electron is?
• Describe two other examples of situations in which measuring something about an object somehow changes it.

Answer 1

Uncertainty principle is a quantum phenomenon it means it is applicable for small(quantum and atomic) sized object predominantly. It is not observable for the macroscopic sized object since measurement in the case of macroscopic object are taken in the range of centimeter and meter scale and uncertainty of measurement with these object are only order of atomic scale while in the case of atomic sized object it will be observable due to small scale measurements .

By considering the uncertainty principle we have

Δx.Δp ~ ℏ/2

by p = h.c/λ

then Δx ∝ Δλ ~ λ

it means by using very short wavelength it will gives you exact position of electron.

and by using very long wavelength there will be large uncertainty in the position of atomic sized objects.Like electron and photons.

Other application of uncertainty Principle:-

This relationship also applies to energy and time, in that one cannot measure the precise energy of a system in a finite amount of time.

ΔE.Δt ~ ℏ/2

This relationship also applies to angular momentum and angular position , in that one cannot measure the angular momentum and angular position of a system.

ΔJ.Δθ ~ ℏ/2