Skip to content
Choose the Best Answer · Q20

Q.If uncertainty in position and momentum are equal, then minimum uncertainty in velocity is

(a) 1mhπ\dfrac{1}{m}\sqrt{\dfrac{h}{\pi}}
(b) hπ\sqrt{\dfrac{h}{\pi}}
(c) 12mhπ\dfrac{1}{2m}\sqrt{\dfrac{h}{\pi}}
(d) h4π\dfrac{h}{4\pi}
Tamil Nadu DgeTextbookSubjectiveImportance★★★★★
27% · 20/73 Questions
🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

Step 1. At the minimum-uncertainty limit, Δx⋅Δp=h4π\Delta x\cdot\Delta p=\dfrac{h}{4\pi}. Given that Δx=Δp\Delta x=\Delta p (call this common value xx), substitute:

x⋅x=h4π⇒x2=h4π⇒x=h4π=12hπx\cdot x=\frac{h}{4\pi}\qquad\Rightarrow\qquad x^2=\frac{h}{4\pi}\qquad\Rightarrow\qquad x=\sqrt{\frac{h}{4\pi}}=\frac12\sqrt{\frac{h}{\pi}}

Step 2. Since Δp=m Δv\Delta p=m\,\Delta v, and Δp=x\Delta p=x from Step 1:

Δv=xm=12mhπ\Delta v=\frac{x}{m}=\frac{1}{2m}\sqrt{\frac{h}{\pi}} …

Unlock everything free for 14 days

  • Full step-by-step solutions
  • Concept-first explanations
  • Methods, shortcuts & mistakes
  • PYQ mapping + timed mock tests

Full access for 14 days. No credit card required.