A2 Physics 物理 出国英语2.5.1 Photoelectric Effect MS.pdfVIP

PhotoelectricEffectAnswers

1.(a)Thefollowingequationdescribesthereleaseofelectronsfromametalsurfaceilluminated

byelectromagneticradiation.

hf=k.e.max+φ

Explainbrieflywhatyouunderstandbyeachofthetermsintheequation.

hfEnergyofaphoton(1)

k.e.maxKineticenergyofemittedelectron/equivalent(1)

φEnergytoreleaseelectronfromsurface/equivalent(1)

(3marks)

(b)Calculatethemomentumpofanelectrontravellinginavacuumat5%ofthespeed

oflight.

p=mv(1)

=9.11×10–31kg×0.05×3×108ms–1(1)

(noecfforincorrectmass)

p=1.37×10–23Ns/kgms–1(1)Unitpenalty

(3marks)

WhatisthedeBrogliewavelengthofelectronstravellingatthisspeed?

6.63×1034

λ=−23ecf(b)(1)

1.37×10

λ=4.84×10–11mUnitpenalty(1)

(2marks)

Whyareelectronsofthiswavelengthusefulforstudyingthestructureofmolecules?

λ/similartosize/spacingatoms/molecules(1)

Diffractionoccurs(1)