Challenging Engineering Problems with Detailed Answers
As compared to planar LED structure, Dome LEDs have power efficiency, effective emission area and a) Greater, lesser, reduced b) Higher, greater, reduced c) Higher, lesser, increased d) Greater, greater, increased 18. In a multimode fiber, much of light coupled in the fiber from an LED is: a) Increased b) Reduced c) Lost d) Unaffected 19. The internal quantum efficiency of LEDs decreasing with temperature. a) Exponentially, decreasing b) Exponentially, increasing c) Linearly, increasing d) Linearly, decreasing 20. In silicon, the thermal energy available at room temperature is enough to cause some electrons to move to the conduction band. State whether the given statement is true or false. a) True b) False 21. At high temperatures, an intrinsic semiconductor material will have more electrons than holes. State whether the given statement is true false. a) True b) False External radiance. 22. In extrinsic silicon, the Fermi energy will be closer to the conduction band when there are more electrons in the conduction band than holes in the valence band. State whether the given statement is true or false. a) True b) False 23. The depletion layer in a pn junction is created by the diffusion of majority free carrier into the adjacent material where there are fewer carriers of that type. State whether the given statement is true or false. a) True b) False 24. The depletion layer in a pn junction contains a large number of free carriers such as electrons and holes. State whether the given statement is true or false. a) True b) False