[{"id":146153,"question":"In which of the following states does the incandescent substance give continuous spectrum?","choices":[{"text":"Vapours in atomic state","value":"A"},{"text":"Vapours in molecular state","value":"B"},{"text":"Solid or fluid in bulk state","value":"C"},{"text":"Solid or fluid in plasma state","value":"D"},{"value":"E"}],"correctAnswer":3},{"id":146152,"question":"Which of the following sources give discrete emission spectrum?","choices":[{"text":"Incandescent electric bulb","value":"A"},{"text":"Sun","value":"B"},{"text":"Mercury vapour lamp","value":"C"},{"text":"Candle","value":"D"},{"value":"E"}],"correctAnswer":3},{"id":146151,"question":"There are discrete energy levels in atoms. It was first experimentally demonstrated by","choices":[{"text":"Rutherford's experiment","value":"A"},{"text":"Franck Hertz experiment","value":"B"},{"text":"Marsden's experiment","value":"C"},{"text":"Somerfield experiment","value":"D"},{"value":"E"}],"correctAnswer":2},{"id":146150,"question":"The essential distinction between X-rays and<span style=\"color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small;\">γ-rays is that</span>","choices":[{"text":"<span style=\"color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small;\">γ-rays have smaller wavelength than X-rays</span>","value":"A"},{"text":"<span style=\"color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small;\">γ-rays emanate from nucleus while X-rays emanate from outer part of the atom</span>","value":"B"},{"text":"<span style=\"color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small;\">γ-rays have greater ionizing power than X-rays</span>","value":"C"},{"text":"<span style=\"color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small;\">γ-rays are more penetrating than X-rays</span>","value":"D"},{"value":"E"}],"correctAnswer":2},{"id":146149,"question":"A photoelectric cell coverts","choices":[{"text":"Electrical energy to light energy","value":"A"},{"text":"Light energy to light energy","value":"B"},{"text":"Light energy to electrical energy","value":"C"},{"text":"Light energy to elastic energy","value":"D"},{"value":"E"}],"correctAnswer":3},{"id":146148,"question":"Ultra-violet radiation of 6.2 eV falls on an aluminium surface. K.E. of fastest electron 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":146147,"question":"When light wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however, light of 600 nm wavelength is sufficient for creating photoemission. What is the ratio of the work functions of the two emitters?","choices":[{"text":"1 : 2","value":"A"},{"text":"2 : 1","value":"B"},{"text":"4 : 1","value":"C"},{"text":"1 : 4","value":"D"},{"value":"E"}],"correctAnswer":2},{"id":146146,"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":146145,"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":146144,"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 1m, the electrons emitted by the photocell","choices":[{"text":"Carry 1/4th their previous energy","value":"A"},{"text":"Are 1/16th 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":146143,"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":146142,"question":"Copper and germanium are cooled to 70K 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":146141,"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 electron 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":146140,"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":146139,"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}]