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Question:
In a hydrogen atom, the electron and proton are bound at a distance of about 0.53 Angstrom:(a) Estimate the potential energy of the system in eV, taking the zero of the potential energy at infinite separation of the electron from proton. (b) What is the minimum work required to free the electron, given that its kinetic energy in the orbit is half the magnitude of potential energy obtained in (a)? (c) What are the answers to (a) and (b) above if the zero of potential energy is taken at 1.06 Angstrom separation?
Answer:

The distance between electron-proton of a hydrogen atom, image198 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

Charge on an electron, q1  image199 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

Charge on a proton, q2 image200 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

1. Potential at infinity is zero.

image201 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

Potential energy of the system, p-e = Potential energy at infinity − Potential energy at distance, d

Where,

image007 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1 is the permittivity of free space

image202 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image203 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image204 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1 Potential enerygyimage205 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

Since image206 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image207 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image204 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1 Potential energyimage208 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image209 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

Therefore, the potential energy of the system is image210 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

2. Kinetic energy is half of the magnitude of potential energy.

Kinetic energyimage211 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

Total energy = image212 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1 = 13.6 eV

Therefore, the minimum work required to free the electron is 13.6 eV.

3. When zero of potential energy is taken, image213 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image204 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1 Potential energy of the system = image214 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image215 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image216 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image101 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image102 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

image103 NCERT Solutions class-12 physics Electrostatic Potentia and Capacitance Part-1

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