MCQ on Crystal Oscillations with Answers

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MCQ on Crystal Oscillations with Answers


Q1. Which of the following statements is NOT correct ?

  • (A) Acoustic branch of diatomic linear chain is similar to the monoatomic case 
  • (B) Both group velocity and phase velocity are equal to the velocity of sound in the long wavelength limit
  • (C) Under the low wavelength limit, the lattice acts as a low pass filter 
  • (D) Acoustic and optical modes in diatomic lattice cancel each other at the boundary of first Brillouin zone

Q2. In the Kronig-Penney model, the discontinuous in the E vs k curve occur on either side of the centre for a k-value equal to (where n = 1, 2, 3, ….)

  • (A) /
  • (B) /2a 
  • (C) √(/2a
  • (D) (2nπ)/a

Q3. Which of the following statements is correct for NaCl crystal structure?

  • (A) It is a simple cubic lattice with one atom basis. 
  • (B) It is a face-centered cubic lattice with one atom basis 
  • (C) It is a simple cubic lattice with two atom basis 
  • (D) It is a face-centered cubic lattice with two atom basis.

Q4. Which of the following is the best technique for measuring the effective mass of an electron in a semiconductor?

  • (A) Resistivity measurements 
  • (B) Cyclotron resonance 
  • (C) X-rays diffraction experiment 
  • (D) Millikan’s oil drop experiment

Q5. Which of the following statements is true about the velocity of electron in an energy band ?

  • (A) It is constant throughout the band 
  • (B) It is maximum at the bottom of the band 
  • (C) It is maximum at the inflection point of the E(k) curve 
  • (D) It is maximum at the top of the band

Q6. In one-dimensional periodic chain of atom with lattice parameter ‘a’ has first brillouin zone at:

  • (A) a 
  • (B) 2a 
  • (C) π/a 
  • (D) /a

Q7. The origin of van der Waal’s interaction in molecular crystal is

  • (A) nuclear 
  • (B) magnetic 
  • (C) Ionic 
  • (D) fluctuating dipolar

Q8. In the Kronig-Penney model, electrons are assumed to be moving in

  • (A) one-dimensional square well potential 
  • (B) one-dimensional square well periodic
  • (C) potential three-dimensional coulomb
  • (D) potential a periodic harmonic potential

Q9. Indicate the false conclusion drawn from the Kronig-Penney model of band theory of

  • (A) the energy spectrum consists of a number of allowed energy bands separated by forbidden regions 
  • (B) the width of allowed energy bands decreases with increasing energy 
  • (C) the width of a particular energy band decreases with increasing binding energy of the solid 
  • (D) the total number of possible wave functions in any energy band is equal to the number of unit cells.

Q10. In the expression for bonding force F(r) = (A/rm) – (B/rn) [ n > m, (A, B) = constant) if n takes the value between 7 and 10, the bonding is called as

  • (A) lonic 
  • (B) Covalent 
  • (C) Metallic 
  • (D) Dipole


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Answer Key (if you find any answer wrong, feel free to Correct us)

01.(D) 06.(C)
02.(A) 07.(D)
03.(D) 08.(B)
04.(B) 09.(B)
05.(C) 10.(C)

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