Assignment Unit -7

7/23/2019 Assignment Unit -7

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ASSIGNMENT (UNIT -7)

1. Defne the term ‘stopping potential’in relation to photoelectric eect ?2. Show the variation o photocurrent with collector plate potential or dierent requencies

ut same intensit! o incident radiation ?". Show the variation o photocurrent with collector plate potential or dierent intensities

ut same requenc! o incident radiation ?

#. $he stopping potential in an e%periment on photoelectric eect is 1.& ' .what is thema%imum (inetic energ! o the photoelectrons emitted ?&. $he ma%imum (inetic energ! o a photoelectron is "e' .what is its stopping potential ?). Show graphicall! how the stopping potential or a given photosensitive surace varies with

requenc! o incident radiation ?

*. +ltraviolet radiations o dierent requencies ν1 and ν

2 are incident on two

photosensitive materials having wor( unctions ,1 and ,2 - ,1 ,2 / respectivel!.$he

(inetic energ! o the emitted electrons is same in oth the cases .which one o the two

radiations will e higher requenc! ?0. ,rite instein’s photoelectric equation .State clearl! the three salient eatures oserved in

photoelectric eect which can e e%plained on the asis o aove equation ?3. $he fgure shows a plot o three curves ac showing the variation o photocurrent vs

collector plate potential or three dierent intensities 41 42 and 4" having requencies ν1

ν2 and ν

" respectivel! incident on a photosensitive surace .

5oint out the two curves or which the incident radiations have same requenc! ut

dierent intensities ?

5hotoelectric current

6ollector plate potential

17.Draw suitale graphs to show the variation o photoelectric current with collector plate

potential ora/ 8 f%ed requenc! ut dierent intensities 41 42 4"

/ 8 f%ed intensit! ut dierent requencies ν1

ν2

ν"

11.5lot a graph showing the variation o stopping potential with the requenc! o incident

radiation or two dierent photosensiti9es materials having wor( unctions ,1 and ,2 - ,1 ,2 /.:n what actors does thea/ Slope and/ 4ntercept o the lines depend ?

12.$he given graph shows variation o photoelectric current with collector plate potential or

dierent requencies o incident radiationsphotoelectric current

a/ ,hich ph!sical parameter is (ept constant or the three curves ?

/ ,hich requencies - ν1

ν2 or ν

" / is the highest ?



6ollector plate potential

1".;igure shows variation o stopping potential -'7 / with the requenc! - ν

/ or twophotosensitive materials <1 and <2 a/ ,h! is the slope same or oth lines ?/ ;or which material will the emitted electrons have greater (inetic energ! or the

incident radiation o the same requenc! ? '7 <1 <2

ν

1#.,rite two characteristic eatures oserved in photoelectric eect which supports the

photon pictures o electromagnetic radiation ?1&.8n electromagnetic wave o wavelength = is incident on a photosensitive surace o

negligile wor( unction .4 the photoelectrons emitted rom this surace have the de>

roglie wavelength =1 prove that = @2mc

h =12

1).$he ollowing graph shows the variation o stopping potential '7 with the requenc! ν o

the incident radiation or two photosensitive metals 5 and Aa/ %plain which metal has smaller threshold wavelength

/ %plain giving reason which metal emits photoelectrons having smaller (inetic energ! '7 5 A

:.& 1 -B 17 1& s>1 /c/ i the distance etween the light source and metal 5 is doule how will the stopping

potential change ?1*. Cadiations o requenc! 171& 9 are incident on two photosensitive suraces 8 and

.;ollowing oservations are recordedSURFACE A : No photoemission takes place

SURFACE B : Photoemission takes place but photoelectrons have zero energ

%plain the aove oservations on the asis o instein’s photo>electric equation .ow

will the oservation with the surace change when the wavelength o incident

radiations is decreased ?

108 proton and an electron have same (inetic energ! .,hich one has greater de>roglie

wavelength and wh! ?



13 write the relationship o de roglie wavelength = associated with a particle o mass m in

terms o its (inetic energ! ? !" show graphicall! the variation o de>roglie wavelength -=/ with the potential - ' / through

which an electron is accelerated rom test .!# de Eroglie wavelength associated with an electron accelerated through a potential

dierence is = .,hat will e its wavelength when the accelerating potential is increased to #

' ?

!!$ 8n electron is accelerated through a potential dierence o 1## ' . what is the de>rogliewavelength associated with it ? $o which part o electromagnetic spectrum does this

wavelength correspond ?!%$fnd the ratio o the de Eroglie wavelength associated witha& protons accelerated through a potential o 120 and

/F E particles accelerated through a potential o )# '2#. Derive an e%pression or the de roglie wavelength associated with an electron

accelerated through a potential ' .Draw a schematic diagram o a locali9ed Ewave descriing

the nature o the moving electron ?2&.or what (inetic energ! a neutron will the associated de>roglie wavelength e 1."2 B 17 >

17

m ?2).8 proton and an alpha particle and an alpha particle are accelerated through the same

potential which o the two hasa/ greater value o de>roglie wavelength associated with it and/ less (inetic energ! ?2*. Draw a schematic diagram o the e%perimental arrangement used ! Davisson and

Germer to estalish the wave nature o electrons .%plain rieH! how the de>roglie relation

was e%perimentall! verifed in case o electrons ?20. $he two lines mar(ed 8 and in the given igure show a plot o de>roglie wavelength =

versus1

√ V where ' is the accelerating potential or two nuclei 12 and "

1

a/ ,hat does the slope o the lines represent ?/ identi! which lines corresponded to these nuclei ?

8 =

1

√ V

23. a/ Determine the de>roglie wavelength o a proton whose (inetic energ! is equal to the

rest mass energ! o an electron .<ass o aa/ proton 10") times that o electron ?/ in which region o e.m spectrum does this wavelength lie ?"7. $he ratio etween the de Eroglie wavelength’s associated through a potential o &12 '

and F E particles accelerated through a potential o I volt is ound to e one .;ind the

value o I ?

Assignment Unit -7

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