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question_answer1) Light of frequency 4.5 times the threshold frequency is incident on photo-sensitive material. If the frequency is halved and intensity is doubled, then the photo-current becomes how many times?
question_answer2) When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are just 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?
question_answer3) The wavelength of \[{{K}_{a}}\] X-rays produced by an X-ray tube is \[\text{0}\text{.76}\overset{\text{o}}{\mathop{\text{A}}}\,\] . Find the atomic number of the anode material of the tube.
question_answer4) When light of intensity\[1W/{{m}^{2}}\]and wavelength\[5\times {{10}^{-7}}m\] is incident on a surface. It is completely absorbed by the surface. If 100 photons emit one electron and area of the surface is\[1c{{m}^{2}}\], then find the photoelectric current (in\[\mu A\]).
question_answer5) Photoelectrons of energy 2eV are emitted from a metal surface when photons of energy 5eV are incident on it. What will be the energy (in eV) of emitted photoelectrons when photons of energy 6eV are incident on it?
question_answer6) Silver has a work function of 4.7 eV. When ultraviolet light of wavelength 100 nm is incident upon it, a potential of 7.7 volt is required to stop the photoelectrons from reaching the collector plate. Find the potential (in volt) required to stop photo electrons when light of wavelength 200 nm is incident upon silver.
question_answer7) A potential difference of 20 kV is applied across an X-ray tube. Find the minimum wavelength (in Å) of X-rays generated.
question_answer8) The \[{{K}_{a}}\] X-ray emission line of tungsten occurs at\[\lambda =0.021nm\]. What is the energy difference (in\[keV\]) between K and L levels in this atom?
question_answer9) The K, L and M energy levels of platinum lie roughly at 78, 12 and\[3keV\]respectively. If the ratio of wavelength of \[{{K}_{a}}\]line to that of \[{{K}_{\beta }}\]line in X-rays spectrum is\[\frac{25}{N}\]. Find N.
question_answer10) The wavelength of \[{{K}_{a}}\]X-ray of an element having atomic number\[Z=11\]to\[\lambda \]. The wavelength of \[{{K}_{a}}\]X-ray of another element of atomic number \[Z'\]is\[4\lambda \]. Then find\[Z'\].
question_answer11) Find the maximum kinetic energy of the photoelectrons ejected when light of wavelength 350 nm is incident on a cesium surface. Work function of cesium\[=1.9\text{ }eV.\]
question_answer12) Electrons in a hydrogen like atom \[(Z=3)\] make transitions from the fourth excited state to the third excited state and from the third excited state to the second excited state. The resulting radiation are incident on a metal plate and eject photoelectrons. The stopping potential for photoelectron ejected by shorter wavelength is 3.95 eV. Find the work function (in eV) of the metal plate.
question_answer13) The electric field associated with a monochromatic beam becomes zero \[1.2\times {{10}^{15}}\]times per second. Find the maximum kinetic energy of the photoelectrons when this light on a metal surface whose work function is 2.0 eV.
question_answer14) A photoelectric current emerging in the circuit of a vacuum photocell when its zinc electrode is subjected to electromagnetic radiation of wavelength 262 nm is cancelled if an external decelerating voltage 1.5 V is applied. Find the magnitude of outer contact potential difference of the given photocell. Work function of zinc metal is 3.74 eV.
question_answer15) The peak emission from a black body at a certain temperature occurs at a wavelength of \[\text{6000}\overset{\text{o}}{\mathop{\text{A}}}\,\]. On increasing its temperature, the total radiation emitted is increased 16 times. These radiation are allowed to fall no metal surface. Photoelectrons emitted by the peak radiation at higher temperature can be bought to rest by applying a potential equivalent to the excitation potential corresponding to the transition for the level \[n=4\]to \[n=2\]in the Bohr's hydrogen atom. The work function of the metal is given by \[\frac{a}{100}\]eV where a is the numerical constant. Find the value of \[\alpha \]. \[[Take:\,He=12420eV-\overset{\text{o}}{\mathop{\text{A}}}\,]\]
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