logo

CuriousTab

CuriousTab

Discussion

Home ‣ Electronics and Communication Engineering ‣ Electronic Devices and Circuits See What Others Are Saying!
  • Question

  • A particular green LED emits light of wavelength 5490, Å, the energy bandgap of the semiconductor material used there is .. h = 6.6 x 10-34 J sec.


  • Options
  • A. 2.26 eV
  • B. 1.98 eV
  • C. 1.17 eV
  • D. 0.74 eV

  • Correct Answer
  • 2.26 eV 

    Explanation
    From Plank equation A particular green LED emits light of wavelength 5490, Å, the energy bandgap of the semiconductor ma joule

    to convert it into electron volt it will be divided by 1.6 x 10-19.

    More questions

    • 1. In a microwave coaxial cable the inner conductor radius is a and inner radius of outside conductor is b. For TE11 mode the cut off wavelength is about

    • Options
    • A. a + b
    • B. p(a + b)
    • C. pa
    • D. pb
      • Discuss
    • 2. A 256 x 4 EPROM has

    • Options
    • A. 8 address pins and 4 data pins
    • B. 8 address pins and 8 data pins
    • C. 4 address pins and 8 data pins
    • D. 4 address pins and 4 data pins
      • Discuss
    • 3. A capacitor stores 0.15C at 5 V. Its capacitance is

    • Options
    • A. 0.75 F
    • B. 0.75 ?F
    • C. 0.03 F
    • D. 0.03 ?F
      • Discuss
    • 4. Loss angle of a good quality cable is about

    • Options
    • A. 1°
    • B. 30°
    • C. 70°
    • D. 90°
      • Discuss
    • 5. If B, H and M denote flux density, field intensity and magnetisation, B = ?0 (H + M).

    • Options
    • A. True
    • B. False
      • Discuss
    • 6. Which one of the following is true for EM wave propagation through rectangular waveguide of cross-section 2a x a

    • Options
    • A. critical wavelength for TE10 mode is the same as that for TE02 mode
    • B. critical wavelength for TE10 mode is one half of that for TE10 mode
    • C. critical wavelength for TE10 mode is the same as that for TM10 mode
    • D. critical wavelength for TE10 mode is double that for TE01mode
      • Discuss
    • 7. Minimum number of 2-input NAND gates required to implement the function F = (x + y) (Z + W) is

    • Options
    • A. 3
    • B. 4
    • C. 5
    • D. 6
      • Discuss
    • 8. The first and second subscripts in models of circular waveguides depict

    • Options
    • A. the number of full sine wave variations in circumference in direction and Bessel function variations in radial direction respectively
    • B. the Bessel function variations in radial direction and the number of full sine wave variations in circumference direction respectively
    • C. the Bessel function variations in circumference direction and number of full sine wave variations in radial direction respectively
    • D. none of the above
      • Discuss
    • 9. Which of the following is not a travelling wave?

    • Options
    • A. e = Em sin (?x - ?t)
    • B. e = Em cos (?x - ?t)
    • C. e = Em sin (?t - ?x)
    • D. e = Em sin (?x)
      • Discuss
    • 10. Consider a loss less antenna with a directive gain of + 6 dB. If 1 mW of power is fed to it the total power radiated by the antenna will be

    • Options
    • A. 4 mW
    • B. 1 mW
    • C. 7 mW
    • D. 1/4 mW
      • Discuss

    Comments

    There are no comments.
Enter a new Comment




Aptitude

Engineering

Programming

Reasoning

Links

Copyright ©CuriousTab. All rights reserved.