NAT I Engineering Physics With Answers

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NAT I Engineering Physics

Sr. # Questions Answers Choice
1 Ultra-violet radiation of 6.2 eV falls on an aluminium surface K.E of fastest electrons emitted is(work function = 4.2 eV) 3.2 x 10-21 J 3.2 x 10-19 J 7 x 10-25 J 9 x 10-32 J
2 The frequency of the incident light falling on a photosensitive metal plate is doubled the kinetic energy of the emitted photoelectrons is Double the earlier value Unchanged More than doubled Less than doubled
3 A monochromatic source of light is placed at a large distance d from a metal surface Photoelectrons are ejected at rate n,kinetic energy being E. If the source is brought nearer to distance d/2, the rate and kinetic energy per photoelectron become nearly 2n and 2E 4n and 4e 4n and E N and 4E
4 A photocell with a constant p.d of V volt across it illuminated by a point source from a distance of 25 cm. When the source is moved to a distance of 1 m, the electrons emitted by the photocell Carry 1/4th their previous energy Are 1/6th as numerous as before Are 1/4th as numerous as before Carry 1/4th their previous momentum
5 Radio waves of constant amplitude can be generated with Rectifier Filter FET Oscillator
6 Copper and germanium are cooled to 70 K from room temperature then Resistance of copper increases while that of germanium decreases Resistance of copper decreases while that of germanium increases Resistance of both decreases Resistance of both increases
7 When n-type of semiconductor is heated Number of electrons increases while that of holes decreases Number of holes increases while that of electrons decreases Number of electrons and holes remains same Number of electrons and holes increases equally
8 The part of a transistor which is heavily doped to produce large number of majority carriers is Emitter Base Collector Any of the above depending on nature of transistor.
9 A p-n junction has a thickness of the order of 1 cm 1 mm 10<sup>-6</sup> cm 10<sup>-12</sup> cm
10 When boron is added as an impurity to silicon the resulting material is n type conductor n type semiconductor p-type conductor p-type semiconductor
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