MCQ on Origin of Quantum Mechanics with Answers

Practice MCQ on Origin of Quantum Mechanics with Answers

MCQ on Origin of Quantum Mechanics with Answers

Q1. A particle of rest mass m0 is moving uniformly in a straight line with relativistic velocity βc, where c is the velocity of light in vacuum and 0 < β < 1. The phase velocity of the de Broglie wave associated with the particle is :

• (A) βc
• (B) c/β
• (C) c
• (D) c2

Q2. The black body spectrum of an object O1 is such that its radiant intensity (i.e. intensity per unit wavelength interval) is maximum at a wavelength of 200 nm. Another object O2 has the maximum radiant intensity at 600 nm. The ratio of power emitted per unit area by O1 to that of O2 is :

• (A) 1/81
• (B) 1/9
• (C) 9
• (D) 81

Q3. The speed of an electron, whose de-Broglie wavelength is equal to its compton wavelength, is (c is the speed of light)

• (A) c
• (B) c/√2
• (C) c/2
• (D) c/2

Q4. If the uncertainty in the location of a particle is equal to its de-Broglie wavelength, then the uncertainty in its velocity V is

• (A) V/2
• (B) V
• (C) V/
• (D) V/3

Q5. The photoelectric threshold for tungsten is 2300 Å. The energy of the electrons emitted from the surface incident on the tungsten (h = 6.63 x 10-34 J-sec) is

• (A) 2.39 x 10-12 joule
• (B) 2.39 x 10-19 joule
• (C) 1.48 x 10-19 joule
• (D) 3.56 x 10-19 joule

Q6. An electron has a speed of 300 m/sec accurate up to 0.01%. With what fundamental accuracy can locate the position of this electron (mass of electron, me = 9.1 x 10-31 kg, charge, e = 1.6 x 10-19 coulomb and Planck’s constant h = 6.64 x 10-34 joules / sec ) ?

• (A) 2.4 cm
• (B) 1.2 cm
• (C) 1.8 cm
• (D) 3.6 cm

Q7. X-rays of 10.0 p.m. are scattered from a target. The maximum energy of the recoil electron (h/mc for electron is 2.426 ×10-12 m) is

• (A) 3.27 x 10-15 joules
• (B) 6.54 x 10-15 joules
• (C) 5.64 x 10-15 joules
• (D) 2.37 x 10-15 joules

Q8. In Compton scattering, wavelength shift is towards

• (A) shorter wavelength
• (B) longer wavelength
• (C) shorter or longer depending on the angle of scattering
• (D) shorter or longer side depending on photon energy

Q9. The photon energy for light of wavelength 3.1 x 10-7 m is [hc = 1.24 x 10-6 eVm]

• (A) 3.1 eV
• (B) 6.2 eV
• (C) 2.4 eV
• (D) 4.0 eV

Q10. The uncertainty relation holds for the following situation

• (A) holds for particles only
• (B) does not hold for microscopic particles
• (C) holds for both microscopic and macroscopic particles
• (D) depends on the nature of the particle

Q11. If the Broglie wavelength of an electron and proton are equal, then

• (A) the velocity of proton is less than that of the electron
• (B) the velocities of proton and electron are equal
• (C) the velocity of proton is greater than that of the electron
• (D) the energy of electron is less than that of the proton

Q12. The position and momentum of a 1 keV electron are simultaneously determined. If its position is located to within 1 Å, what is the percentage of uncertainty in its momentum?

• (A) 0.61
• (B) 6.17
• (C) 61.73
• (D) 0.061

Q13. The photoelectric equation is derived under the assumption that

• (A) electrons are associated with waves of wavelength λ = h/p where P is the momentum
• (B) light is emitted only when electrons jump between the orbits
• (C) light is absorbed in quanta of energy E = hν
• (D) light behaves like a wave

Q14. The number of electrons emitted increases if the incident light has

• (A) higher frequency
• (B) higher wavelength
• (C) higher intensity
• (D) lower frequency

Q15. The photoelectric threshold for a metal is 3000 Å. The kinetic energy of an electron ejected from it by radiation of wavelength 1200 Å is

• (A) 3.1 eV
• (B) 12.6 eV
• (C) 6.2 eV
• (D) 21.4 eV

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