Photoelectric Effect Questions and Answers

1 1 2 2 3 3 4 4 4 Five elements A B C D and E have work functions 1 2 eV 2 4 eV 3 6 eV 4 8 eV and 6 eV respectively If light of wavelength 4000 is allowed to fall on these elements then photoelectrons are emitted by 1 A B and C 2 A B C D and E 4 Only E 15 3 A and B A Carnot engine with sink s temperature at 17 C 14 15 1 1 2 2 A B C D i E 1 2 eV 2 4 eV 3 6 eV 4 8 eV a 6 eV 4000 Aff fl 1 A BUC 3 AB gta 3 3 eft 2 A B C D E 4 E arm 50 fi

A totally reflecting small plane mirror placed horizontally faces a parallel beam of light as shown in figure The mass of mirror is 20 gm Assume that there is no absorption in the lens and that 30 of the light emitted by source goes through lens Find the power of source in MW needed to support the weight of mirror g 10 m sec mirror 28 30 30x180x1 18 To 54

18 When ultraviolet light of wavelength 100 nm is incident upon a sample of silver metal a potential difference of 7 7 volt is required to stop the photoelectrons from reaching the collector plate The potential required to stop photo electrons when light of wavelength 200 nm is incident upon silver is 1 1 5 V 2 1 85 V 3 1 95 V 4 2 37 V

electron is accelerated through a potential difference v 1 of its kinetic energy converts into on X ray photon which falls on a photosensitive plate The maximum kinetic energy of the photoelectron is observed to be four times the work function The de Broglie wavelength associated with the photoelectrons should be 1 h 2mvoe 2 5 h 2mv e N3 5 5 h 2mv e

In an experiment on photoelectric effec t a photon is incident on an electron fr om one direction and the photoelectron is emitted almost in opposite direction Does this violate conservation of mom entum

1 2 Question Type Single Correct Type 3 Retarding 4 O A C D Potential V Accelerating Beam B has highest frequency Photoelectrons ejected by beam B have momentum greater than C and less than A Beam A has the highest rate of photoelectric emission Beam C has longest wavelength

A photosensitive metallic surface has work function Eo If photons of energy 5E0 fall on this surface the electrons come out with a maximum velocity of 4 x 106 m s When the photon energy is changed to 2Eo then maximum velocity of photo electrons will be Question Type Single Correct Type 1 2 3 4 2 x 107 m s 2 x 106 m s 8 x 107 m s 8 x 106 m s

If light of wavelength 3100 is used in the experiments then following graph is observed Photocurrent A Threshold wavelength is 620 nm C Threshold wavelength is 310 nm 2 ol Potential involts B An electron may be emitted with KE lev in the above experir D An electron may be emitted with KE 4eV in the above experi

The maximum velocity of emitted by light of wavelength the surface of a metal of work function is Question Type Single Correct Type 1 2 3 2 hc Xo mx 2 hc Xo m 1 2 1 2 an electron A incident on 2 hc xo m

Q No 100 The wavelength Ae of an electron and Ap of a photon of same energy E are related by 1 2 3 Correct Answer 2 Your Answer 3 por 1 1 Ap Ap A Ap XA Ap x

The light photons of energy 1 eV and 2 5 eV respectively are made incident on metallic plate of work function 0 5 eV one after another The ratio of maximum kinetic energy of photoelectron emitted by them will be 113 0 116 D

Photoelectric emission is observed from a metallic surface for frequencies v and v of V2 the incident light rays v V If the maximum values of kinetic energy of the photoelectrons emitted is the two cases are in the ratio of 1 k then the threshold frequency of the metallic surface is Question Type Single Correct Type 1 2 3 V1 V2 K 1 kv 22 K 1 Kv V K 1

Exercise 1 Electrons are accelerated by the voltage U 150 V Calculate the wavelength of the electrons e 1 6 10 C m 9 1 10 kg h 6 625 103 J s Exercise 2 The angular spread of a particular laser beam is 0 10 rad Calculate the

When monochromatic radiation of intensity I falls on a metal surface the number of photoelectron and their maximum kinetic energy are N and T respectively If the intensity of radiation is 21 the number of emitted electrons and their maximum kinetic energy are respectively 1 2N and T 2 2N and 2T 3 N and T

Consider the two following statements I and II and identify the correct choice given in the answers 1 In photovoltaic cells the photoelectric current produced is not proportional to the intensity of incident light 2 In gas filled photoemissive cells the velocity of photoelectrons depends on the wavelength of the incident radiation Both 1 and 2 are true Both 1 and 2 are false

15 For ion of metal match the following colum A B C Line Column 1 Slope of line 1 Slope of line 2 Line 2 Colume P Q 6 c Value of X D Value of X 1 A R B S C P D Q 2 A R B S C Q I 3 A S B R C P D Q 4 A S B R C Q I R h S h e

experiment is carried out in which li one on a photocell whose plate cathode work function of 1 5 eV Two seri easurements were performed For the easurement light has a wavelength 41 d intensity I and for the second measure ght has a wavelength of 517 5 nm mensity 31 The ratio of stopping potenti wavelength is Take h 4 14 x 10 2 5 3 3

In an experiment on photoelectric effect of the incident radiation is of the incident radiation is red wavelength wavelength tord of the initial value and the maxi kinetic energy of the photoelectron is obse to be n times the previous value The thres wavelength for the metal plate is 1 3 3 n 1 n 3 4 n 3 32 n

Find the maximum magnitude of the linear momentum of a photoelectron emitted when light of wave length 400 nm falls on a metal having work function 2 5 eV 1 4 x 10 Kg m s 2 8 x 10 25 Kg m s 3 12 x 10 25 Kg m s

In a photoelectric effect experiment photons of energy 13eV are incident on a metal of work function 0 9 eV due to which photoelectrons are emitted from metal Energy of the photoelectrons are sufficient to excite a H atom from its ground state then A Kinetic energy of emitted photoelectron may be 12 1 eV B Kinetic energy of emitted photoelectron may be 10 2 eV C In subsequent emission spectrum of H atom eihter 1 or 2 or 3 spectral lines will be present D Maximum possible stopping potential is 12 1 volt

d 20 Let K be the maximum K E of photo electrons emitted by light of wavelength A and and K coresponding to wavelength A If K 2K then 1 2 A 2 2 4 2 3 2 Two masses of 10 kg and 201

Determine the number of photons emitted p wavelength 650 nm and has a power output a 6 54 10 5 photons s b 5 23 10 7 photons s c 3 834 10 6 photons s d 9 29 10 4 photons s Answer A B C

2 2 2 Photoelectrons are observed to just emit out of a material surface when the light of 620 nm falls on it with the intensity of 100 W m2 If the light of wavelength 400 nm is incident on the same material with an intensity of 1 W m2 what would be the minimum reverse potential needed to stop the outflow of the electrons 2 d 1 1 V 3 1 2 V 2 2 V 4 1 9 V

Suppose that a ray of blue colour is emitted during the transition of electron from n 6 to n 4 in He Which electronic transition in Balmer series of hydrogen atom would emit the same colour A B C D 6 4 4 2 5 3 3 2 4

Please give explaination for correct answer and why not rest option plea se explain each option with reason a nd diagram Figure shows four situations in which charged particles are moving in electric field In which of the following cases the de Broglie wavelength of particle is decreasing E Roth 1 and 2 E E

A solar cell consists of a very light thin plane surface which can absorb all the photons incident on it Consider such a cell placed at a very large distance from the sun normal to the direction of incident radiation If the mass per unit area in mg m of the cell such that it will neither be blown away nor be pulled in by the sun is 778k then find k

2 2 Photoelectrons are observed to just emit out of a material surface when the light of 620 nm falls on it with the intensity of 100 W m If the light of wavelength 400 nm is incident on the same material with an intensity of 1 W m2 what would be the minimum reverse potential needed to stop the outflow of the electrons 1 1 V 3 1 2 V 2 2 V 4 1 9 V

When monochromatic radiation of intensity and frequency falls on a surface number of photoelectron and their kinetic energy are N and T respectively If frequency of a monochromatic radiation is doubled keeping intensity same the number of photons and their maximum kinetic energy will become A N and 2T B C 2N and T 2N and 2T D None of above Asked by 3454549 aesl id Standard XII Stream NEET Jul 26 2021 10 45 F Add your responses

Example 6 Ultraviolet light of wavelength 350 mm and intensity 1 00 W m is directed at a potassium surface If 0 50 of the incident photons produce photoelectrons how many photoelectrons are emitted per second if the potassium surface has an area of 1 00 cm

LION A photoelectrons produced by a monochromatic light beam incident on a metal surface have a spread in their kinetic energies Reason R The work function of metal varies as a fur from the surface 1 Point a Both A and Ra correct explanatio PT b Both A and R are true but R is NOT the correct explanation of A c A is true but R is false

The threshold wavelength of a certain metal is 6600 A The photoelectric work function for the metal will be 3 x 10 m s Th 6 6 x A O 14 x 10 1 J B O 3x10 J C O 2x 10 1 J D O 4x 10 9 J

The collector plate in an experiment on photoelectric effect is kept vertically above the emitter plate Light source is put on and a saturation photocurrent is recorded An electric field is switched on which has a vertically downward direction Which of the following is are incorrect A The photocurrent will increase B The kinetic energy of the electrons will increase C The stopping potential will decrease D The threshold wavelength will increase

6 362x10 19 J 226 eV 2ma Example 2 An electron is confined in a cubical box of side 1A 1 Find its lowest energy ii what is the temperature at which the average of the molecule of a perfect gas would be equal to the lowest energy of the electron k 1 38 10 23 J K Energy of the electron E2 1 1 E1 2 1 E1 1 2

The work function of metal A atomic number x and metal B atomic number y are 4 3 eV and 3 1 eV respectively The ratio of slopes of the stopping potential versus frequency plot for metal A to that of metal B is 4 3 3 1 y

Example 25 In a Stern Gerlach experiment a collimated beam silver atom is produced by vapourising silver salt in a furnace at 1200 C If the beam travels 100cm use uncertainty principle to find the order of magnitude of the smallest spot that can be recorded on the detector Given Planck s constant h 6 6x10 34 Js Boltzmann constant k 1 4 10 23 J K Mass of hydrogen

Photoelectrons are emitted from a given metal surface when it is illuminated by two beams P and Q of light both having the same frequency The saturation value of the photocurrent produced by P has a magnitude which is four times that produced by Q The ratio of the electric field strength in beam P to that in Qis A B 1 4 1 2 C 2 D 4

All electrons ejected from a surface by incident light of wavelength 200 nm can be stopped before travelling 1 m in the direction of uniform electric field of 4 N C The work function of the surface is faga de at 200 nma va tas fe and an geag 4 N C falli 1 m n o Hod an vu i H U I G OPTIONS MARK FOR REVIEW CLEAR SELECTION OA 4 eV OB 6 2 V OC 2 eV

COLLISION LOSS OF K E PROBLEM A metal ball of mass 2 kg moving with speed of 36 km h has a head on collision with a stationary ball of mass 3 kg If after collision both the balls move as a single mass then the loss in K E due to collision is a 100 b 140 c 401 d 601

Light of wavelength 500 nm is incident on a met li with work function 2 28 eV The de Broglie wavelength of the emitted electron is 1 2 8 x 10 2m 2 2 8 x 10 10m 3 2 8 x 10 m 4 2 8 x 10 9 m A photoelectric surface is illuminated successively by of unuglength and 2 2 If the

The threshold wavelength for photoelectric 27 emission from a material is 5200 Photo electrons will be emitted when this material is illuminated with monochromatic radiation from a A 50 watt infrared lamp B 50 watt ultraviolet lamp C 1 watt ultraviolet lamp D B and C both

Light of frequency 1 5 times the threshold frequency is incident on a photosensitive material What will be the photoelectric current if the frequency is halved and intensity is doubled Question Type Single Correct Type 1 2 3 zero doubled four times

4 In photoelectric effect stopping potential is 3 volt and wavelength used is wavelength of light becomes 22 then stopping potential becomes 1 volt Find threshold wavelength a 12420 A b 6070 c 24840 A d none

9 Photons with energy 5 eV are incident on a cathode C in a photoelectric cell The maximum energy of emitted photoelectrons is 2 eV When photons of energy 6 eV are incident on C no photoelectrons will reach the anode A if the stopping potential of A relative to Cis a 3 V b 4 V c 1 V d 3 V

Which of the following statements is correct regarding the photoelectric effect experiment The photocurrent increases with intensity of light of a given frequency Stopping potential increases with increase in intensity of incident light of a given frequency The photocurrent increases with increase in frequency of light of a given intensity All of these

70 The work function for metal X Y and Z are 2 5 eV 4 28 eV and 3 3 eV respectively The maximum kinetic energy of electrons emitted from the respective metal surfaces are in order if energy of incident photon Ephoton 5eV is same for all cases 1 kx ky kz 3 ky kz kx 2 kx kz ky 4 kx ky kz

d number of electrons emitted is a quarter of the initial number 16 Light of wavelengths falls on a metal having work he A function Photoelectric effect will take place only a 2 b c 2222 d 47

2 Choose correct relation for given i and V graph i photoelectric current V Accelerating potential difference A1 A2 Wavelengths of incident light 1 2 2 3 2 A 2 21 22 4 22 RK CO NA

mivien two polarisers a 30 b 45 c 22 5 d 60 88 Light from sodium lamp is made to pass through two polaroids placed one after the other in the path of light Taking the intensity of the incident light 100 the intensity of the out coming light that ca be varied in the range a 0 to 100 d 0 to 25 b 0 to 50 d 0 to 75 39 From Brewster s law except for poli

6 A plano convex lens is made of flint glass Its focal length is a inversely proportional to the wavelength of light b longer for red than for blue c longer for blue than for red d the same for all colours

30 180 The work function of a surface of a photosensitive material is 9 0 eV The wavelength of the incident radiation for which the stopping potential is 3 V lies in the X ray region Visible region Ultraviolet region Infrared region