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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता १२ वी

Using the expression for the radius of orbit for the Hydrogen atom, show that the linear speed varies inversely to the principal quantum number n the angular speed varies inverse - Physics

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प्रश्न

Using the expression for the radius of orbit for the Hydrogen atom, show that the linear speed varies inversely to the principal quantum number n the angular speed varies inversely to the cube of principal quantum number n. 

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उत्तर

According to Bohr’s second postulate,

mrnvn = `"nh"/(2pi)`

∴ `"m"^2"v"_"n"^2"r"_"n"^2 = ("n"^2"h"^2)/(4pi^2)` 

∴ `"v"_"n"^2 = ("n"^2"h"^2)/(4pi^2"m"^2"r"_"n"^2)`

Substituting, rn = `(epsilon_0"h"^2"n"^2)/(pi"m""Ze"^2)` in above relation,

`"v"_"n"^2 = ("n"^2"h"^2)/(4pi^2"m"^2) xx ((pi"m""Ze"^2)/(epsilon_0"h"^2"n"^2))^2`

= `("n"^2"h"^2)/(4pi^2"m"^2) xx (pi^2"m"^2"Z"^2"e"^4)/(epsilon_0^2"h"^4"n"^4)`

= `("Z"^2"e"^4)/(4epsilon_0^2"h"^2"n"^2)`

∴ `"v"_"n"^2 ∝ 1/"n"^2`

⇒ `"v"_"n" ∝ 1/"n"`

Expression for angular speed:

Since, vn = rn ω and rn = `(epsilon_0"h"^2"n"^2)/(pi"m"_"e""e"^2)`

∴ `omega = ("v"_"n")/"r"_"n" = (("e"^2)/(2epsilon_0"h")) 1/"n"/(epsilon_0"h"^2"n"^2)/(pi"m"_"e""e"^2)`

∴ `omega = "e"^2/(2epsilon0"hn") xx (pi"m"_"e""e"^2)/(epsilon_0"h"^2"n"^2) = ((pi"m"_"e""e"^4)/(2epsilon_0^2"h"^3)) 1/"n"^3`

⇒ `omega ∝ 1/"n"^3`

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पाठ 15: Structure of Atoms and Nuclei - Long Answer

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