Photoelectric Effect Questions and Answers

The plots of intensity versus wavelength for three black bodies at temperature T T2 and T3 respectively are as shown in figure their temperature are such that O T T T3 O T T T O T T T T T T3 O

velength of matter waves is also determined by using kinetic energy as formula is h 2mE If you double the kinetic energy of a particle how does the deBroglie wavelength change OPTIONS A 2 1 707 A 1 A 2 0 707 X 1 A 2 1 5 A 1

Ho 7 View In English A black body is at a temperature of 5760 K The energy of radiation emitted by the body at wavelength 250 nm is U at wavelength 500 nm is U and that at 1000 nm is U3 Wien s constant b 2 88 100 Which of the following is correct 2 3 Correct Answor 4 Your Answor 3 Status incorrect U 0 U3 0 U U 24

Viow In English An intense light source radiate uniformly in all directions At a distance of 5 0 m from the source the radiation pressure on the perfectly absorbing surface is 9 0x10 6 Pa What is total average power output the source 1 3 4 649 KW 630 KW 849 KW 830 KW Conton D

1 32x cm s Sodium and Copper have work functions 2 3 eV and 4 5 eV respectively Then the ratio of the threshold wavelengths is nearest to 1 1 2 2 4 1 3 2 1 4 1 4 2 32 cms 3 cm s 4 32 n ecms

lustration 7 Light quanta with an energy 4 9 eV eject photoelectrons from metal with work function 4 5 eV Fir the maximum impulse transmitted to the surface of the metal when each electron flies out olution

In scenario C visible light is yellow Determine its wavelength frequency and energy per photon frequency In scenario D visible light has a photon energy of 4 274 x 10 9 J Determine its wavelength frequency and color frequency wavelength energy per photon wavelength The visible light in scenario D is

3 An X ray photon of frequency 3 10 19 Hz collides with a free electron a rest and is scattered at 60 degrees Find the direction in which the electron will move 1 Point 30 degrees 54 34 degrees 35 66 degrees

YOU DIDN T ATTEMPT Three photons of energy 5eV 6eV 7eV are incident on metal having work function 3eV The maximum kinetic energy of emitted photoelectrons is 2eV 3eV 4eV CORRECT ANSWER

Fant Size A TA TA The work function of copper surface is 45 eV The threshold wavelength for photoelectric effect from the surface of copper is Planck s constant h 6 63 x 10 HJs speed of light in vacuum c 3 x 10 m s charge of an electron e 16 x 10 9 C D Click here to view this option Ref No 241491

parallel plates are connected across the terminal of 100 V power supply These plates have a fine hole at the centre An electron having energy 200 eV is so directed that it passes through the holes When it comes out its de Broglie wavelength will be nearly

JULI mature or kadiation and Matter The threshold wavelength of lithium is 8000 When light of wavelength 9000 is made incident on it then the photoelectrons 1 Will not be emitted 2 Will be emitted 3 Will sometimes be emitted and sometimes not 4 Nothing can be said

notons with a wavelength of 459 nm in air enter a plate of crown glass with index of refraction n 1 52 Find the speed wavelength and energy of a photon in the gl HINT a speed in m s m s b wavelength in m c energy in J m

velocities of the photo electrons coming out are V and v respectively then 1 2 3 V V 4 V V 2h 1 1 m f f 2h f f m 1 mv hf 2 2h m f f 2h 71 2 Official Ans by NTA 1 1 mv hf 1

1 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 1 2 2 3 3 4 4 5

Figure shows some energy levels of an electron in H atom E Which among the following transitions produces photon of wavelength in visible region of electromagnetic spectrum E E E3 E2 wwwww E5 E4

The voltage applied to an X ray tube is 9 kV The mass corresponding to maximum energy of photon emitted by X ray tube will be 1 6 10 1 kg 1 6x10 32 kg 3 2 x 10 27 kg 16x 10 20

5 volt In the photoelectric experiment if we use a monochromatic light the 1 V curve is as shown If work function of the metal is 2 eV estimate the power of light used in W Assume efficiency of photo emission to be 10 3 ie number of photoelectrons emitted are 10 of number of photons incident on metal 10 A Marks Obtained 00 Answer 7 Solution all bett Time Spent 44 sec

Two metallic plates P and Q are separated by a distance of 0 1 M These are connected through an ideal ammeter as shown in the figure A magnetic field B exists parallel to the plates A light of wavelengths between 4000 and 6000 fall on the plate Q whose work function is 2 39 eV Find the minimum value of magnetic field B for which the current registered by the ammeter is zero X X X X X Cow

12 Radiation of two photons having energies twice and five times the work function of a metal are incident successively on the metal surface The ratio of the maximum velocity of photoelectrons emitted in the two cases will be a 1 2 XC 1 4 b 2 1 d 4 1

Determine the initial energy of the photon MeV Round your result to 3 decimal place Answer MeV on eat b Calculate the maximum energy loss AE in MeV if this gamma ray photon would be scattered o electron Round your result to 3 decimal place

27 The energy flux of sunlight reaching the surface of the earth is 1 388 x 10 W m How many photons nearly per square metre are incident on the Earth per second Assume that the photons in the sunlight have an average wavelength of 550nm 1 2 51 10 2 3 84 10 1 21

The de Broglie wavelength and kinetic energy of a particle is 2000 and 1 eV respectively If its kinetic energy becomes 1 MeV then its de Broglie wavelength becomes Question Type Single Correct Type 1 1 2 2 3 5 A 10

The potential difference between the plates of a parallel plate capacitor is changing at the rate of 106 V s If the capacitance is 2uF the displacement current in the dielectric of the capacitor will be 1 1 A 2 2 A 3 3 A

When light of frequency 2v and intensity Lilluminates a metal in a photoelectric experiment the stopping potential is 2 V and saturation current is 3 mA Now If the frequency is reduced to one fourth and intensity is doubled the new stopping potential and saturation current are respectively vo is the threshold frequency 1 0 5 V 6 mA 2 0 5 V 3 mA 3 2 V 6 mA 4 0 0

A parallel beam of electromagnetic radiation of wavelength 200 nm is incident on a perfectly reflecting surface The power incident on 1 mm area is 5 x 10 watts Find the pressure exerted by the radiation

The relation between time and displacement for two particles is given by y 0 06 sin 2 0 04t q Y 0 03 sin 2 1 04t The ratio of the intensity of the waves produced by the vibrations of the two particles will be 2 1 1 2 4 1

nucleon E against the nuclear mass M A B C D E F correspond to different nuclei Consider four reactions i A B C E ii C A B iii D E F iv F D E Eb where is the energy released In which reactions is positive A C DE M LL

In a Compton scattering experiment the wavelength of the incident photon is 65 0 pm and the wavelength of the scattered photon is 69 0 pm Calculate the kinetic energy of the recoiling electron O a 2 07 eV O b 1 65 keV O c 0 8 keV O d 4 1 keV e 1 11 kev

Photons with energy 5 eV are incident on 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 C is 1 1 V 2 3 V 3 3 V 4 4 V

When a photon of wavelength 3000 A is incident on a metal surface an electron of energy 0 5 eV is emitte If a photon of wavelength of 2000 A is incident on the metal surface then the energy of emitted electron w be 1 0 5 eV 2 More than 0 5 eV 3 Less than 0 5 eV 4 None of the above

3 A piece of metal has a cutoff wavelength of Acutoff 450 mm Consider illuminating this piece of metal with two different wavelengths of light a 1 500 nm beam and a A2 400 nm beam For each of the two beams find a The maximum kinetic energy of ejected electrons b What is their speed What is their de Broglie wavelength 3

A parallel beam of monochromatic light of wave length 500 nm is incident normally on a perfectly absorb surface The power through any cross section of the beam is 10 W Find a Number of photon absorb by surface per second b The force exerted by light beam on the surface C

If threshold wavelength for a photosensitive plate is 4000 A what will be the value of saturation current if radiation of wavelength 5000 is incident 1 Zero 2 1 mA 3 3 mA 4 Data is insufficient to predict

When you shine 300 nm light on an electrode surface photoelectrons are emitted How many of the metals from the table might the electrode be Explain Potassium 2 30 eVSodium 2 75 eVAluminum 4 28 eVTungsten 4 55 eVCopper 4 65 eVlron 4 70 evGold 5 10 eV JAWNHO 1 2 3 4 5

22 Find the number of electrons emitted per second by a 24 W source of monochromatic light of wavelength 6600 A assuming 3 efficiency for photoelectric effect take h 6 6 10 4 Js 1 48 10 9 2 48 10 7 F 3 3 8 1019 4 24 x 10 7

You shine a monochromatic light with a wavelength of 207 nm on a metal surface The maximum kinetic energy of the electrons emitted from the metal is 6 4x10 19 J What is the work function of the metal O 1 6 10 19 J O 3 2x10 19 J 9 6x10 19 J O 6 4 10 19 J O 1 1x10 18 J

Silver has a work function fo 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 The potential required to stop photo electrons when light of wavelength 200 nm is incident upon silver is A skipped B C 1 5 V 1 85 V 1 95 V 6 7 Correct 0 Wrong 1 MY PERFORMANCE SCORE 1 00 out of 32 F OL

A light detector has an absorbing area of 4 0 x 106 m and absorbs 40 of the incident light which is at wavelength 500 nm The detector faces an isotropic source 10 m from the source The energy E emitted by the source versus time t is given in the figure here E 7 8 nJ t 2 5 s At what rate are photons absorbed by the detector E nJ E 0 N s 1 v

3 Light with an energy flux of 20 W cm falls on a non reflecting surface at normal incidence If the surface has an area of 30 cm the total momentum delivered for complete absorption during 30 min is a 36 x 10 5 kg m s b 36 x 104 kg m s c 108 x 104 kg m s d 1 08 107 kg m s

24 The magnetic field associated with a light wave is given at the origin by 0 B B sin 3 14 x 107 ct sin 6 28 107 ct If this light falls on a silver plate having a work function of 4 7 eV what will be the maximum kinetic energy of the photo electrons c 3 108 ms h 6 6 10 34 J s 9 Jan 2019 Evening A 7 72 eV B 8 52 eV D 6 82 eV C 12 5 eV

2 Find the photon energy in units of electron volts of electromagnetic waves of wavelength 40m a 3 10 8 eV c 3 2x10 8 eV b 3 1x10 8 eV d 3 3 10 8 eV

c 106 W d 107 W 3 A perfectly reflecting mirror has an area of 1 cm Light energy is allowed to fall on it for 1 h at the rate of 10 W cm2 The force that acts on the mirror is a 3 35 x 10 8 N b 6 7 x 10 8 N c 1 34 x 10 7 N d 2 4 x 104N 4 The pressure exerted by an a electromagnotio 1

A sample of hydrogen atoms is irradiated with light with wavelength 86 8 nm and electrons are observed leaving the gas Each hydrogen atoms were initially in its ground level Choose the correct option s Given mass of electron 9 x 10 1 kg The maximum kinetic energy of photoelectrons is 0 7 eV approx The de Broglie wavelength of photoelectrons is greater than wavelength of incident photons The de Broglie wavelength of photoelectrons is greater than that of bound electrons in H atom The magnitude of momentum of incident photons is more than momentum of ejected photoelectrons

8 If velocity of a galaxy relative to earth is 1 2 x 10 ms then increase in wavelength of light from galaxy as compared to the similar source on earth will be a 0 3 b 0 4 d 0 6 c 0 5

1 What is the the frequency in kHz of gamma ray radiation that has a wavelength of 0 01516 nanometers The speed of light is 3 00x10 m s 8 Key Concept Frequency v and wavelength A of light are inversely related to each other by c A v where c is the speed of light

6 The photoelectric threshold wavelength of a certain metal is 3000 If the radiation of 2000A is incident on the metal a Electrons will be emitted b Positron will be emitted c Protons will be emitted d Electrons will not be emitted

n 60 The threshold frequency for a certain photosensitive metal is v When it is illuminated by light of frequency V 2v the maximum velocity of photoelectrons is V What will be the maximum velocity of the photoelectrons when the same metal is illuminated by light of frequency v 5v a 2vo b 2vo c 2 2v d 4v

photo sensitive surface is receiving light of wavelength 5000 at the rate of 10 7 Js The number of photons ejected per second is a 2 5 10 2 b 2 5 10 1 c 2 5 101 d 2 5 10

to 45 The collector of the photocell in photoelectric experiment is made of tungsten while the emitter is of platinum having work function of 10 eV Monochromatic radiation of wavelength 124A and power 100 watt is incident on emitter which emits photo electrons with a quantum efficiency of 1 The accelerating voltage across the photocell is of 10 000 volts Use h 12400 eV Platinum emitter Radiation 124 A V 10 000 V 3 What is the power sunnli 11 Tungsten target 275