Photoelectric Effect Questions and Answers

Question No In the circuit shown in figure if the diode forward voltage drop is 0 3 V then the voltage difference between A and B is 5 KQ www B 5 km www A 0 2 mA O 1 3 V 0 5 V O 2 3 V Zero Co

Photons of energy 7 eV are incident on two metals A and B with work functions 6 eV and 3 eV respectively The minimum de Broglie wavelengths of the emitted photoelectrons with maximum energies are 1 and 2 respectively where 1 2 is nearly A 0 5 B C D skipped 1 4 4 0 2 0 G 1 6 Correct C MY PERF SCO 1 out o

In a photo electric experiment under condition of saturation current we consider two different cro section A B as shown VA and vg represents average speed of electrons at two cross sections A B A iAiB B VA VB D VA VB e Ht

The L S and Jquantum numbers corresponding to the ground state electronic configuration of Boron Z 5 are a L 1 S 1 2 J 3 2 c L 1 S J 11 2 2 b L 1 S J 2 2 3 3 d L 1 S 5 J 2 2

A beam of mono energetic particles having speed v is described by the wave function y x u x exp ikz where u x is a real function This corresponds to a current density a u x v b v c zero d u x

Monochromatic light of wavelength 300 nm is incident normally on a surface of area 4cm If the intensity of light is 150 milliwatt m which photons strike the surface O 9 1 x 10 3 photon per sec O 8 1 x 10 photon per sec O 6 2 x 1015 photon per sec 03x 1021 photon per sec Determine the rate at Marks 4 1

A proton and an o particle are accelerated through the same potential difference The ratio of de Broglie wavelength Ap to that is NCERT Pg 400 1 2 1 2 2 1 3 2 2 1 4 1 2 2 a sc 3 Davi 4 Com 11 Which a Sh no 2 Inter 3 Pol 4 Ma

4 1 10 m s An electron is moving with an initial veloci V val enters in a uniform magnetic fie A B Then its de Broglie waveleng INGERT Pg 40 1 Increase with time 2 Decrease with time 3 Remains constant 4 Increases and decreases

In a photoelectric experiment the stopping potential V versus applied frequency v graph for three different metals A B C are as shown The metal with maximum threshold wavelength is V ABC

A hydrogen atom initially at rest and free to move in the second excited state It comes to ground state by emitting a photon then the momentum a hydrogen atom due to recoil is 1 12 1 x 10 27 Kg ms 1 X 2 6 45 10 27 Kg ms 1 3 3 x 10 27 Kg ms 1 4 1 5 10 27 Kg ms 1

In a black body radiation at certain temperature T 1 the wave length having maximum intensity of radiation equals 9000A When the temperature is increased from TitoT the total radiation increases 16 times The peak radiation at T is found to be capable of ejecting photoelectrons The maximum kinetic energy of photoelectrons is the same as the energy of photon that one gets when one of electron in the M shall of hydrogen atom jumps to L shell the work function of the metal will be

Violet light can cause photoelectric emission from a metal but blue light cannot If sodium light is incident on the metal then A The photoelectric current decreases B The number of photoelectrons ejected per second increases C The velocity of photoelectrons increases D No photoelectric emission occurs E The photoelectric current increases

Question No 13 The potential at a point A is 10 V and at another point B is 12 V An electron free to move in the region passes point A with a kinetic energy of 5 eV When it passes through B its kinetic energy will be Options 7 eV 10 eV 5 eV 12 eV

42 An electron in the hydrogen atom jumps from excited state n to the ground state The wavelength so emitted illuminates a photosensitive material having work function 2 75 eV If the stopping potential of the photoelectron is 10 V then the value of n is b 2 a 5 c 3 d 4 CBSE Final 2011

19 Choose the correct statement for the given i photoelectric current and V accelerating potential difference graph where and 2 are wavelengths of incident light 1 2 2 3 2 2 V V 2 0 V 2 2 2 4 22

work functions 2 0 eV d 2 5 eV and 3 0 eV respectively A light beam containi Photoelectric effect experiments are performed using three different metal plates p q and fl wavelengths of 550 nm 450 nm and 350 nm with equal intensities illuminates each of the plates T correct I V graph for the experiment is JEE 200 A r P V B A r V C Ja r V D X r q

No 2 View In English An X rays tube operates at 20 KV A particular electron loses 5 of its kinetic energy to emit an X rays photon at the first collision The wavelength corresponding to this photon will be 1 2 3 Correct Answer 1 Status unattempted 124 nm 2 24 nm 3 5 nm zero 4

5 terms of temperature are given below 1500 T AP k 10 5 e 1000 BQ K 10 4 e T If initially t 0 both reaction started with same initial concentration of A and B then at what temperature both the reaction will have same initial NCERT Pg 112 Trate 1 217 C 3 500 C 2 217 K 4 500 K

beam of white light is incident on glass air interface from glass to air such that green light just suffers total internal reflection The colours of the light which will come out to air are a violet indigo blue b all colours except green c yellow orange red d white light 2004

Electromagnetic radiations of longest wavelength is Radio waves Visible radiation Infrared radiation hr min OT Rays

4 4 Maximum work is required to move q in figure c The de Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T Kelvin and mass m is h 3mkT 1 2h 2 3mkT 2h 3 mkT Two blocks A and Ro 4 h mkT 0 8

5 In an experiment on photoelectric effect the stopping potential is measured for monochromatic light beams corresponding to different wavelengths The data collected are as follows wavelength nm 350 400 450 500 550 stopping potential V 1 45 1 00 0 66 0 38 0 16 Plot the stopping potential against inverse of wavelength 1 2 on a graph paper and find a the Planck constant b the work function of the emitter and c the threshold wavelength

An electron mass m with initial velocity vector v voi Voj is in an electric field vector E Eok If Xo is initial de Broglie wavelength of electron its de Broglie wave length at time t is given by 1 3 2 2 e E t m v 20 e E t 2m vo 2 2 4 20 e E t m v 20 e Et m v

When a monochromatic point source of light is at a distance of 0 2 m from a photoelectric cell the cut off voltage and saturation current are respectively 0 6 V and 18 0 mA If the same source placed 0 6 m away from the photoelectric cell then 1 The stopping potential will be 0 2 V 2 The stopping potential will be 0 6 V 3 The saturation current will be 2 0 mA

3 Let P and E denotes the linear momentum an energy of photon If the wavelength is decreased 1 Both P and E decrease 2 Both P and E increase 3 P increase and E decrease 4 P decrease and E increase photone er second

A photoelectric cell is illuminated by a point source of light 1 m away When the source is shifted to 2m then 1 each emitted electron carries one quarter of the initial energy 2 number of electrons emitted is half the initial number 3 each emitted electron carries half the initial energy 4 number of electrons emitted is a quarter of the initial number

Which of the following statements are incorrect about the photoelectric effect A The kinetic energy of photo electron depends on nature of metal The number of photoelectrons in proportional to the energy of light incident The kinetic energy of photoelectron is proportional to the intensity of light Highly electropositive metals like cesium can easily exhibit photoelectric effect B CL

Online Mock Test Series for NEET 2020 15 Two different radiations having wavelength less than threshold wavelength are incident on similar t photoelectric cells If both cells are receiving same energy per second per unit area then saturation current is 1 Higher for low frequency radiation 2 Higher for high frequency radiation 3 Same for both radiation 4 Zero for both radiation

11 A graph regarding photo electric effect is shown between the maximum kinetic energy of electrons and frequency of the incident light On the basis of data shown in graph the work function Take h 6 4 x 10 34 Js Kmax ev 8 4 2 2 T 10 20 30 x 10 4 Hz

emitted due to Maximum kinetic energy of photoelectron from the surface of work function incidence of light of frequency v is E If the frequency of incident light is doubled then maximum kinetic energy of emitted photon will be 1 2E bilenet big 2 2E O 3 2E O 4 2E 20

4 All the three are possible 5 Sodium and copper have work functions 2 3 eV and 4 6 eV respectively Then the ratio of their threshold wavelengths is nearest to 2 2 1 4 4 1 1 1 2 3 1 4

Two particles A and B are in motion If the wavelength associated with particle A is 5 x 10 8 m calculate the wavelength associated with particle B if its momentum is half of A 5x 10 8 n 1 2 3 4 O 10 5 cm 10 7 cm 5 x 10 8 cm

If a source of power 4kW produces 1020 1 3 4 Correct Answer 2 Your Answer 4 Status incorrect v rays X rays Ultraviolet rays Microwaves photons second the radiation belongs to part of the spectrum called

Ans 1 35 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 1 zero 2 doubled 3 four times 4 one fourth

In a photoelectric experiment a parallel beam of monochromatic light with power of 200 W is incident on a perfectly absorbing cathode of work function 6 25 eV The frequency of light is just above the threshold frequency so that the photoelectrons are emitted with negligible kinetic energy Assume that the photoelectron emission efficiency is 100 A potential difference of 500 V is applied between the cathode and the anode All the emitted electrons are incident normally on the anode and are absorbed The anode experiences a force F n x 10 N due to the impact of the electrons The value of n is Mass of the electron 10 31 kg and 10 1610 18 1

2 21 The maximum kinetic energy of the photoelectrons ejected will be eV when light of wavelength 350 nm is incident on a cesium surface Work function of cesium 1 9 eV

In a photoelectric effect experiment for a certain cathode material stopping potential V as a function of frequency f of light used is shown What is the wo function in eV of the material V Volts 2 10 1 OT I 0 25 0 5 0 75 f 10 Hz

5 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 1 3 1 IN 2 4 2 113 116 4

Radiation of wavelength Ao 3 being the threshold wavelength is incident on a photosensitive metallic sphere of radius R The charge developed on the sphere when electrons cease to be emitted will be Question Type Single Correct Type 1 2 3 4 Rhc e 6 Rhc e 8 Rhc e o

measurement shows that all the ejected electrons have nonzero kinetic energy What can you say about the photelectric current Cannot predict the state of photoelectric current Photo current decreasing electric is Photelectric current is saturated Photelectric current

A parallel beam of photons of intensity I strike a plane surface at angle 45 to the surface If plane surface have reflection coefficient 0 5 then pressure exerted by the beam on the surface C is speed of light is Question Type Single Correct Type 1 2 31 4C 31 2C

20 In a standard photoelectric emission set up the metal has threshold wavelength 22 where is the wavelength of incident radiation The accelerating potential is such that it increases the kinetic energy of the photoelectrons by 200 before striking the anode The de Brogie wavelength of the fastest electrons before striking anode is h Planks constant m mass of electron c speed of light 1 3 h 2mc 22h 2 4 h 3mc h

The cut off wavelength for a metal is 5000A When light of wavelength 3000 falls on it the maximum kinetic energy of the ejected photoelectron is E When light of wavelength 2000 falls on it the maximum kinetic energy of the photoelectrons will be 1 4E 3 2 5F 2 3E 4 2 25E

Question If power of the source wavelength of light surface area and photoelectric efficiency of the metal of the plate are adjusted to 60 W 6000 0 04 m and 10 4 respectively Which of the following statements are correct Use hc 0 12420 eV A This question has multiple correct options Range of kinetic energy of photoelectrons does not depend on

Why iss the second option correct Bcoz number of photo electrons depends on intensity not v right Correct graphs regarding photo electric effect is are Kinetic energy 11 L Number of photo electrons Number of photo electrons Intensity of radiation All of these

Example A rod is moving with speed w r t ground such that velocity of rod is parallel to its length C An observer is also running in the same direction with speed G5 w r t ground If rest length of the rod is L Find the apparent length of the rod as measured by the observer

Example An equilateral triangle is moved parallel to its plane in two ways In first case it is given a speed 3c parallel to bisector of angle 2 C parallel to one of its sides and in second case it is given a speed Find ratio of apparent area in the two cases

17 Light with an energy flux of 18 W cm on a non reflecting surface at normal incidence If the surface has an area of 20 cm Find the average force exerted on the surface during a 30 min time span a 1 2 x 10 6 N b 2 4 x 10 6 N d 6 2 x 10 6 N c 4 8 x 10 6 N

9 A sheet of silver is illuminate by monochromatic ultraviolet radiations of wavelength 1810 What is the maximum energy of the emitted electron The threshold wavelength of silver is 2640 a 9 16 eV b 2 16 eV c 3 16 eV d 4 16 eV

Photoelectric effect experiments are performed using three different metal plates p q and r having work functions p 2 0 eV q 2 5 eV and r 2 0 eV q 2 5 eV and or 3 0 eV respectively A light beam containing wavelengths of 550 nm 450 nm and 350 nm with equal intensities illuminates each of the plates The correct I V graph for the experiment is 2009 A Take hc 1240 eV nm B C P q V q V D P r I P r Ab V V