7/29/2019 P3 - Homework Week 11 - Questions

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P3-Homeworkweek11[RevisionProblems]

Youmayusethefollowinginformation:

Chargeofproton=1.60210-19CChargeofelectron=-1.60210-19C

Massofproton=1.67310-27kgMassofneutron=1.67510-27kgPlancksconstant=6.6310-34m2kgs-1

1)a)Explainwhatismeantbyanisotope

b)TheincompletetablebelowshowsinformationfortwoisotopesofUranium

Numberof

protons

Numberof

neutrons

Specificcharge

ofnucleus/.FirstIsotope 92 143

SecondIsotope 3.7107

Copythetableinyouranswersheetand

i)writedowntheunitforthespecificchargeintheheadingofthelastcolumnofthetable.

ii)intheabovetable,writedownthenumberofprotonsinthesecond

isotope.Writedownclearlyhowyoucalculatedthisnumber. iii)calculatethespecificchargeofthefirstisotopeandwritethisinthe

table.Writedownclearlyhowyoucalculatedthisnumber.

iv)calculatethenumberofneutronsinthesecondisotopeandputthisnumberinthetable.

2)Whenmonochromaticlightshinesuponametalsurface,electronsareemitted

fromthesurfaceasdescribedbythephotoelectriceffect. a)Statewhatismeantbythresholdfrequencyinthecontextofthe

photoelectriceffect.

b)Stateanddescribetheeffectontheemittedelectronsif i)thefrequencyofthelightisincreased.

ii)theintensityofthelightisincreased.

c)Thethresholdfrequencyoflithiumis5.51014

Hz.Calculatetheworkfunctionoflithium.

d)Whatisthemaximumkineticenergyoftheemittedelectronswhenlightoffrequency6.21014Hzisincidentonthesurfaceofasampleoflithium?

3)Awirewithcross-sectionaldiameterof2mmismadefromcopper.Copperhas1.101029freeelectronspermetrecubed.Whatisthevalueofthecurrent

flowingthroughthewirewhenthedriftspeedofelectronsis0.093mms-1?

Answers:

1)b)ii)92iii)3.65107iv)1462)c)3.6510-19Jd)4.610-20J

3)5.15A

7/29/2019 P3 - Homework Week 11 - Questions

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