As you asking for the Question Paper of the Modern Physics of the VTU University the Question Paper is given below

Modern Physics

II Blackbody radiation spectrum, maximum intensity is shifting towards
A) shorter wavelength B) longer wavelength C) no change D) none of these

III Group velocity of wave is equal to
A) V phase B) V particle C) Velocity of light D) none of these

IV de-Broglie wavelength of an electron accelerated by a potential of 60 V is
A) 1.85 Å B) 1.58 Å C) 1.589 Å D) 1.57 Å

b. Describe Davisson-Germer experiment to prove the dual nature of matter waves.

c. Explain phase velocity and Group velocity. Derive de-broglie wavelength using Group velocity. (4+8+8)

1 a. 1) The de-Broglie wavelength associated with an electron of mass m and accelerated by a potential V is

2) Davisson and Germer were the first to demonstrate :
i) The straight line propagation of light ii) The diffraction of photons
iii) The effective mass of electron iv) None of these

3) Electrons behaves as waves because they can be :
i) Deflected by an electric field ii) Diffracted by a crystal
iii) Deflected by magnetic field iv) They ionize a gas

4) In Davisson-Germer experiment, the hump is most prominent when the electron is accelerated by
i) 34 volts ii) 54 volts iii) 60 volts iv) 80 volts (04 Marks)
b. Define phase velocity and group velocity. Show that group velocity is same as particle velocity. (08 Marks)
c. Derive de-Broglie wavelength using Group velocity. (04 Marks)
d. Compare the energy of a photon with that of a neutron when both are associated with wavelength of 1 Å. Given that mass of neutron is 1.678 × 10 -27 kg. (04 Marks)

1 a. i) An electron and a proton are accelerated through same potential. The ratio of de-Broglie wavelength e/p is

ii) Wavefunction associated with a material particle is
A) Single valued B) Finite C) Continuous D) ALL the above

iii) In a blackbody radiation spectrum, the maximum energy peaks shift towards the shorter wavelength side with the increase in temperature. This confirms
A) Stefan’s law B) Wein’s law C) Rayleigh-Jean’s law

D) Planck’s law
iv) The group velocity of the particle is 3×106 m/s, whose phase velocity is
A) 6.06×106 m/s B) 3×1010 m/s C) 3 nm/s D) 1.5×1010 m/s (04 Marks)

b. Describe Davisson and Germer experiment for confirmation of deBroglie hypothesis.
(08 Marks)

c. Explain phase and group velocity. Calculate the de-Broglie wavelength of a bullet of mass 5 gm moving with a velocity 20 km/hr. (08 Marks)

1 a. i) Wien’s law is deduced from Planck’s radiation formula under the condition of
A) Very small wavelength and temperature B) Large wavelength and temperature
C) Small wavelength and high temperature D) Large wavelength and small temperature

ii) The Compton wavelength is given by
A) h/m0C2 B) h2/m0C2 C) h/m0C D) h2/2m0C

iii) Which of the following relations can be used to determine de-Broglie wavelength associated with a particle?
iv) If the group velocity of a particle is 3×106 m/s, its phase velocity is
A) 100 m/s B) 3×106 m/s C) 3×108 m/s D) 3×1010 m/s