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question_answer1) Surface of certain metal is first illuminated with light of wavelength \[{{\lambda }_{1}}=350nm\] and then, by light of wavelength \[{{\lambda }_{2}}=540nm.\] It is found that the maximum speed of the photo electrons in the two cases differ by a factor of (2) The work function of the metal (in eV) is (Energy of photon\[=\frac{1240}{\lambda (in\,\,nm)}eV\])
question_answer2) The magnetic field associated with a light wave is given at the origin by \[B={{B}_{0}}[sin(3.14\times {{10}^{7}})ct+sin(6.28\times {{10}^{-7}})ct].\] If this light falls on a silver plate having a work function of 4.7 eV, what will be the maximum kinetic energy (in eV) of the photoelectrons? \[(c=3\times {{10}^{8}}m{{s}^{-1}},h=6.6\times {{10}^{-34}}J-s)\]
question_answer3) A metal plate of area \[1\times {{10}^{-4}}{{m}^{2}}\] is illuminated by a radiation of intensity \[16\text{ }mW/{{m}^{2}}.\] The work function of the metal is 5 eV. The energy of the incident photons is 10 eV and only 10% of it produces photo electrons. The number of emitted photo electrons per second is \[\left[ 1\,\,eV=1.6\times {{10}^{-19}}J \right]\]
question_answer4) The stopping potential \[{{V}_{0}}\] (in volt) as a function of frequency (v) for a sodium emitter, is shown in the figure. The work function (in eV) of sodium, from the data plotted in the figure, will be : (Given: Planck's constant \[\left( h \right)=6.63\times {{10}^{-34}}Js,\] electron charge \[e=1.6\times {{10}^{-19}}C\])
question_answer5) If the de Broglie wavelength of an electron is equal to \[~{{10}^{-3}}\] times the wavelength of a photon of frequency \[6\times {{10}^{14}}\] then the speed (in m/s) of electron is equal to: (Speed of light \[=3\times {{10}^{8}}m/s\]) Planck's constant \[=6.63\times {{10}^{-34}}J.s\] Mass of electron \[=9.1\times {{10}^{-31}}kg\])
question_answer6) In a photoelectric experiment, the wavelength of the light incident on a metal is changed from 300 nm to 400 nm. The decrease in the stopping potential (in V) is \[\left( \frac{hc}{e}=1240nm-V \right)\]
question_answer7) A particle A of mass 'm' and charge 'q' is accelerated by a potential difference of 50v another particle B of mass '4m' and charge 'q' is accelerated by a potential differnce of 2500V. The ratio of de - Broglie wavelength \[\frac{{{\lambda }_{A}}}{{{\lambda }_{B}}}\] is
question_answer8) In a Frank - Hertz experiment, an electron of energy 5.6 eV passes through mercury vapour and emerges with an energy 0.7 eV. The minimum wavelength (in nm) of photons emitted by mercury atoms is
question_answer9) In the arrangement shown in figure, y =1.0 mm, d= 0.24 mm and D = 1.2 m. The work function of the material of the emitter is 2.2 eV. If stopping potential is 0.3x, then value of x (in V) is
question_answer10) The electric field of light wave is given as \[\overrightarrow{E}={{10}^{3}}\cos \] \[\left( \frac{2\pi x}{5\times {{10}^{-7}}}-2\pi \times 6\times {{10}^{14}}t \right)\hat{x}\frac{N}{C}\] This light falls on a metal plate of work function 2eV. The stopping potential (in V) of the photo-electrons is: Given, \[E\,(\text{in}eV)=\frac{12375}{\lambda \,(\text{in}\,\overset{\text{o}}{\mathop{\text{A}}}\,)}\]
question_answer11) In a photoelectric effect experiment the threshold wavelength of light is 380 nm. If the wavelength of incident light is 260 nm, the maximum kinetic energy (in eV) of emitted electrons will be: Given \[E(in\,\,eV)=\frac{1237}{\lambda (in\,\,nm)}\]
question_answer12) A 2 mW laser operates at a wavelength of 500 nm. The number of photons that will be emitted per second is : [Given Planck's constant \[h=6.6\times {{10}^{-34}}Js,\] speed of light \[c=3.0\times {{10}^{8}}m/s\]]
question_answer13) A monochromatic source of light operating at 200W emits \[4\times {{10}^{20}}\] photons per second. Find the wavelength (in nm) of the light.
question_answer14) Light of wavelength 180 nm ejects photoelectron from a plate of a metal whose work function is 2 eV. If a uniform magnetic field of \[5\times {{10}^{-5}}\] T is applied parallel to plate, what would be the radius (in metre) of the path followed by electrons ejected normally from the plate with maximum energy?
question_answer15) A 100 W point source emits monochromatic light of 1 wavelength \[6000\,\overset{\text{o}}{\mathop{\text{A}}}\,\]. What is the total number of photons emitted by the source per second?
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