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. : "Modern Physics"

Bohr Model

Q- In the Bohr model of the hydrogen atom, the speed of the electron is approximately 2.20 X 106 m/s. Find

(a) The force acting on the electron as it revolves in a circular orbit of radius 0.530 X 10-10 m and

(b) The centripetal acceleration of the electron.

Solution:

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Momentum of a laser pulse

Q- A pulsed laser fires a 1000-MW pulse horizontally at a 10mg mass suspended vertically from a 4 cm long fiber of negligible mass. If the pulse lasts duration of 200 nanoseconds, and the radiation is completely absorbed by the mass, by what maximum angle is the pendulum deflected?

Solution:

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Potential Well

Q- The longest wavelength line in the spectrum emitted by an electron trapped in an infinitely deep square well is 610 nm. What is the width of the well?

Solution:

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Hydrogen Atom

Q- The normal hydrogen atom consists of a proton nucleus and an orbital electron. Assume that the electron orbit is circular and that the constant distance between the proton and electron is 5.3 x 10-11 m.

(a) What is the force of attraction between the two fundamental particles?

(b) What is the o…

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Relativity: Work and momentum

Q- (a) How much work is required to accelerate a proton from rest to a speed of 0.998 c.

      (b) What would be the momentum of this proton.

Solution:

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de Broglie Wavelength

Q- What is the wavelength of an electron of energy (a) 20 eV (b) 200 eV (c) 2.0 keV

Solution:

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Relativity

Q- What is the percentage change in momentum of a proton that accelerates from (a) 0.45c to 0.80c and (b) 0.80c to 0.98 c.

Solution:

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Photoelectric Effect

Q- The threshold wavelength for emission of electrons from a given surface is 320nm.

a) What will be the maximum kinetic energy of ejected electrons when the wavelength of the incident light is changed to 350nm.

b) What will be the maximum kinetic energy of ejected electrons when the wavelength of…

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Hubble law

Q- The tenth brightest member of the cluster of galaxies known as 'Abell1185' has a brightness of 2.70*1010 Wm-2. A line in its spectrum at a wavelength of 503.1 nm is identified as being a member of the Balmer series that has a rest wavelength of 486.1 nm. Consider the luminosity of the tenth brigh…

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Compton Effect

Q- X-rays of 0.200 nm are scattered off a carbon atom. Scattered x-rays are detected at an angle of 600 relative to the incident beam. Determine

a) The Compton shift

b) The kinetic energy of the recoiling carbon nucleus in eV.  

Solution:

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Photoelectric Effect

Q1- 445 nm light strikes a metal, resulting in a stopping potential V1. 410 nm light strikes the same metal, resulting in a second stopping potential V2. If V1 = 0.70V2, calculate the work function of the metal.

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