I-I and MID I Objective Questions - Past Paper

## Choose the correct answers 1. The work function of a metal is 4.2eV calculate the threshold frequency of a metal is - a. 1.06 X 10¹⁴ - b. 1.06 X 10^-14 - c. 1.06 X 10¹⁵ - d. 1.06 X 10^-15 2. When an electron is accelerated by a potential...

## Choose the correct answers 1. The work function of a metal is 4.2eV calculate the threshold frequency of a metal is - a. 1.06 X 10¹⁴ - b. 1.06 X 10^-14 - c. 1.06 X 10¹⁵ - d. 1.06 X 10^-15 2. When an electron is accelerated by a potential V volts, the de Broglie wavelength is given by - a. 12.26/√V nm - b. 26.12/√V A° - c. 12.26/√V µm - d. 12.26/√V A° 3. If ΔΕ and At are the uncertainties in the measurement of energy and time of a system According to Heisenberg's uncertainty principle - a. ΔΕ. At ≥ h /4π - b. ΔΕ. At ≤ h /4π - c. ΔΕ. At ≥ h /2π - d. ΔΕ. At ≤ h /2π 4. If E1 is the energy value for the ground state of an electron in a one-dimensional potential well of length L, the energy of the first excited state is equal to - a. E1 - b. 2 E1 - c. 4 E1 - d. 9 E1 5. The lowest energy state of a particle of mass m in one-dimensional box of length L is - a. h/8mL - b. h²/8mL - c. h²L²/8m - d. h²/8mL² 6. The velocity of an electron in a periodic field is maximum at of the band - a. Top - b. Bottom - c. Middle - d. Top & Bottom 7. In case of particle in one dimensional box, probability to find an electron is always minimum At a distance of - a. a=0 - b. a=1/2 - c. a=3/2 - d. a=2/3 8. According to classical free electron theory the electrical conductivity of metal is - a. σ = neτ/m - b. σ = ne²τ/m - c. σ = ne³τ/m - d. σ = ne⁴τ/m 9. The density of electrons in the conduction band are equal to the density of holes in the valence band for Semiconductor - a. Intrinsic - b. Extrinsic - c. P-type - d. N-type 10. Solar cell converts energy to energy - a. Light, electrical mechanical - b. Mechanical, electrical - c. Light, light - d. Mechanical, 11. Which of the following can be used as voltage regulator - a. LED - b. Zener - c. P-N junction diode - d. Photo diode 12. At T=0K, the valence band of semiconductor has full of electrons and conduction band of semiconductor has - a. full of electrons - b. no electrons - c. partially filled with electrons - d. partially filled with holes 13. Which of the following is an example of direct band gap semiconductor - a. Ge - b. Si - c. GaAs - d. Sn 14. In PIN diode the photo current Ip is - a. Ip =q.Ne - b. q.N²e - c. Ne/q - d. qnNe/t 15. The barrier potential of Ge is - a. 0.03V - b. 0.07V - c. 0.7V - d. 0.3V 16. The phenomenon that occurs in a PN junction diode when a reverse voltage is applied across it is - a. Zener break down - b. cut in break down - c. Avalanche break down - d. knee break down 17. The only polarization which depends on temperature is - a) Electronic charge - b) lonic - c) Orientational - d) Space 18. Polarization per unit applied electric field is called - a. electric susceptibility - b. magnetic susceptibility - c. electric polarization - d. dielectric constant 19. The unit of porization vector - a. Coulomb/m - b. Coulomb/m³ - c. Coulomb-m - d. coulomb/m² 20. Dielectrics are - a. metals - b. semiconductors - c. insulating materials - d. none ## Fill in the blanks 21. Stefan-Boltzmann's law can be expressed as E=σT⁴ 22. The electrical conductivity of a semiconductor at absolute zero temperature is zero 23. Davisson and Germer experiment supports the concept of wave nature of matter particles. 24. Silicon is a indirect band gap semiconductor. 25. First Brillouin zone extends from -π/a to π/a 26. The recombination produces a layer, at P-N junction, is called depletion layer 27. The possibility of a particle penetrating the barrier from one side to the other side is known as tunneling effect 28. The thickness of the upper layer of a solar cell should be less than 1 diffusion length of a charge carrier. 29. In PIN diode the current produced is mainly due to Photoelectrons 30. The average distance covered by the charge carrier before getting recombine is called diffusion length 31. The hemispherical shape of the LED cap is employed to avoid total internal reflection. 32. During reverse bias, the PIN diode acts as a variable capacitor due to widening of the depletion region. 33. Momentums of both electron and hole should match to have radiative recombination. 34. 1.8eV will be the least energy gap should a LED have to produce visible light. 35. The current that flows due to reverse bias in a photo diode under no light condition is called dark current 36. The photodiode should be operated in reverse bias 37. Pyroelectric materials are the dielectrics that produce polarization when subjected to uniform Heating or cooling 38. The material that can be polarized is called dielectric 39. Dielectric constant is the ratio of permittivity of the medium to the permittivity of free space. 40. The lag of polarization over electric field is called Ferro electric hysteresis