641 Thermions are________________? Physics Medium Full question → A protons B positrons C electrons D photons
642 Which one of the following has the greatest energy gap ? Physics Medium Full question → A insulator B conductor C semi conductor D any of above
643 The velocity of an oscillating charge as it moves to and fro along a wire is always_____________? Physics Medium Full question → A constant B zero C changing D infinite
644 Identify the correct statement about minority carriers_____________? Physics Medium Full question → A holes in n-type and free electrons in p-type B holes in n-type and p-type C free electrons in n-type and holes in p-type D free electrons in n-type and p-type
645 In n-p-n transistor, p works as______________? Physics Medium Full question → A collector B emitter C base D any of above
646 p-n junction when reversed biased acts as a_______________? Physics Medium Full question → A capacitor B inductor C on switch D off switch
647 Semi-conductor germanium and silicon are_________________? Physics Medium Full question → A pentavalent B trivalent C divalent D tetravalent
648 Electrons present in p-type material due to thermal pair generation are_____________? Physics Medium Full question → A majority carriers B minority carriers C dual carriers D blockers
649 The velocity of laser light is___________________? Physics Medium Full question → A Less than ordinary light B More than ordinary light C Equal to ordinary light D Different for different colours or frequency
650 Reflecting mirrors in laser is used to______________? Physics Medium Full question → A Further stimulation B Lasing more C For producing more energetic lasers D All
651 In He-Ne laser the lasing action is produced by_______________? Physics Medium Full question → A Ne only B He-Ne both C Electrons of He D Electrons Ne
652 The metastable state for an atom in laser light is_____________? Physics Medium Full question → A 10-4 sec B 10-5 sec C 10-3 sec D 10-8 sec
653 In laser production the state in which more atoms are in the upper state than in the lower one is called_____________? Physics Medium Full question → A Metal stable state B Normal state C Inverted population D All the above
654 In normal state of energy the incident high energy photons will be______________? Physics Medium Full question → A Stimulated B Absorbed C Cause X-ray emission D Cause laser production
655 Electron cannot exist in the nucleus it is confirmed by observing that______________? Physics Medium Full question → A It does emit radiation B Its size as compare to proton and neutron is very small C No antiparticle of electron is present D The velocity of electron must be very high according to uncertainty principle
656 Wave-like characteristic of electron is demonstrated by______________? Physics Medium Full question → A Line spectrum of atoms B Production of x-rays. C Diffraction by crystalline solids D Photoelectric effect
657 UV radiation can be produced by______________? Physics Medium Full question → A Heating the filament B Electron excitation in the gas C Ionization of atoms D All the above
658 X-rays are diffracted by a crystal but not by a diffraction grating because_____________? Physics Medium Full question → A The ions in a crystal are well arranged B The lines in a diffraction grating cannot reflect X-rays. C The penetration power of X-rays is high in a diffraction grating D The wavelengths of X-rays are of the same order of magnitude as the separation between atoms in a crystal
659 Maximum frequency in the spectrum from X-ray tube is directly proportional to the______________? Physics Medium Full question → A Number of incident electron i.e. filament current B The kinetic energy of the incident electron i.e. the potential difference through which they are accelerated C The soft target which can easily emit electrons D All of above are correct
660 The minimum wavelength of X-rays produced by the bombardment of electrons on the screen of a television set where the accelerating potential is 2.0K V will be______________? Physics Medium Full question → A 6.2 x 10-10m B 9.1 x 10-18m C 3.11 x 10-10m D 4 x 10-10m