[{"id":15629,"question":"Ultra-violet radiation of 6.2 eV falls on an aluminium surface K.E of fastest electrons emitted is(work function = 4.2 eV)","choices":[{"text":"3.2 x 10-21 J","value":"A"},{"text":"3.2 x 10-19 J","value":"B"},{"text":"7 x 10-25 J","value":"C"},{"text":"9 x 10-32 J","value":"D"},{"value":"E"}],"correctAnswer":1},{"id":15628,"question":"The frequency of the incident light falling on a photosensitive metal plate is doubled the kinetic energy of the emitted photoelectrons is","choices":[{"text":"Double the earlier value","value":"A"},{"text":"Unchanged","value":"B"},{"text":"More than doubled","value":"C"},{"text":"Less than doubled","value":"D"},{"value":"E"}],"correctAnswer":3},{"id":15627,"question":"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","choices":[{"text":"2n and 2E","value":"A"},{"text":"4n and 4e","value":"B"},{"text":"4n and E","value":"C"},{"text":"N and 4E","value":"D"},{"value":"E"}],"correctAnswer":3},{"id":15626,"question":"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","choices":[{"text":"Carry 1/4th their previous energy","value":"A"},{"text":"Are 1/6th as numerous as before","value":"B"},{"text":"Are 1/4th as numerous as before","value":"C"},{"text":"Carry 1/4th their previous momentum","value":"D"},{"value":"E"}],"correctAnswer":2},{"id":15625,"question":"Radio waves of constant amplitude can be generated with","choices":[{"text":"Rectifier","value":"A"},{"text":"Filter","value":"B"},{"text":"FET","value":"C"},{"text":"Oscillator","value":"D"},{"value":"E"}],"correctAnswer":4},{"id":15624,"question":"Copper and germanium are cooled to 70 K from room temperature then","choices":[{"text":"Resistance of copper increases while that of germanium decreases","value":"A"},{"text":"Resistance of copper decreases while that of germanium increases","value":"B"},{"text":"Resistance of both decreases","value":"C"},{"text":"Resistance of both increases","value":"D"},{"value":"E"}],"correctAnswer":2},{"id":15623,"question":"When n-type of semiconductor is heated","choices":[{"text":"Number of electrons increases while that of holes decreases","value":"A"},{"text":"Number of holes increases while that of electrons decreases","value":"B"},{"text":"Number of electrons and holes remains same","value":"C"},{"text":"Number of electrons and holes increases equally","value":"D"},{"value":"E"}],"correctAnswer":4},{"id":15622,"question":"The part of a transistor which is heavily doped to produce large number of majority carriers is","choices":[{"text":"Emitter","value":"A"},{"text":"Base","value":"B"},{"text":"Collector","value":"C"},{"text":"Any of the above depending on nature of transistor.","value":"D"},{"value":"E"}],"correctAnswer":1},{"id":15621,"question":"A p-n junction has a thickness of the order of","choices":[{"text":"1 cm","value":"A"},{"text":"1 mm","value":"B"},{"text":"10<sup>-6</sup> cm","value":"C"},{"text":"10<sup>-12</sup> cm","value":"D"},{"value":"E"}],"correctAnswer":3},{"id":15620,"question":"When boron is added as an impurity to silicon the resulting material is","choices":[{"text":"n type conductor","value":"A"},{"text":"n type semiconductor","value":"B"},{"text":"p-type conductor","value":"C"},{"text":"p-type semiconductor","value":"D"},{"value":"E"}],"correctAnswer":4}]