the work function for metallic caesium is 2.14 eV.calculatethe KINETIC ANERGY an
ID: 684784 • Letter: T
Question
the work function for metallic caesium is 2.14 eV.calculatethe KINETIC ANERGY and the SPEED of the electrons ejected by lightof wavelength a) 580 and b) 250.(answer is: a) no kinetic energy and no speed andb) 0.452 a J and 996 km s-1) please show work. the work function for metallic caesium is 2.14 eV.calculatethe KINETIC ANERGY and the SPEED of the electrons ejected by lightof wavelength a) 580 and b) 250.
(answer is: a) no kinetic energy and no speed andb) 0.452 a J and 996 km s-1) please show work.
Explanation / Answer
I assume you mean 580 nm E_photon = h*c/ = (6.626e-34 J*s)*(3e8 m/s)/(580 e-9 m) *(1 eV/1.602e-19 J) = 2.139 eV ~ 2.14 eV KE = E_photon - Work function = 2.14 - 2.14 = 0. = > so nokinetic energy KE = 0.5m*v^2 => If KE = 0, v = 0 b) E_photon = h*c/ = (6.626e-34 J*s)*(3e8 m/s)/(250 e-9 m) *(1 eV/1.602e-19 J) = 4.963 eV ~ 4.96 eV KE = 4.96 - 2.14 = 2.82 eV v = (2*KE/m)^0.5 = (2*2.82 eV *(1.602e-19 J/1eV) / 9.11 e-31kg)^0.5 = 9.95 x 105 m/s Note 1 J/kg = m2/s2 You get m/sbecause you then take a square root
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