Q. Consider that an electron is revolving in an excited state of Hydrogen atom with velocity $\sqrt{25.6}\times10^5$ m s⁻¹. The radius of the orbit is $x\times10^{-9}$ m. The value of x is: [Take the mass of electron to be $9\times10^{-31}$ kg, charge of electron = $-1.6\times10^{-19}$ C and $\frac{1}{4\pi\varepsilon_0}=9\times10^9$ N m² C⁻²]

A) 1
B) 4
C) 3
D) 2
Explanation

[Solution from source] Coulomb force gives the centripetal force: $r=ke^2/(mv^2)$. $v^2=2.56\times10^{11}$, $ke^2=2.304\times10^{-28}$, $mv^2=2.304\times10^{-19}$, so $r=1.0\times10^{-9}$ m and x = 1. Answer (1).

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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