QJEEM19Che3e8: JEE Main 2019 Chemistry - Class 11 JEEM19Che3e8 Solution: What is the work function of the metal if the light of…

Question

Verified Solution • 2025–26 Session moderate

What is the work function of the metal if the light of wavelength 4000

\overset{\circ}{A}

generates photoelectrons of velocity 6

\times

10⁵ ms^–1 from it ?
(Mass of electron = 9

\times

10^–31 kg;
Velocity of light = 3

\times

10⁸ ms^{$-$ 1}
Plank's constant = 6.626

\times

10^–34 Js;
Charge of electron = 1.6

\times

10^–19 JeV^–1)

Accepted Answer

E =

ϕ

+ K.E

\Rightarrow

h

ν

=

ϕ

+

\frac{1}{2} m v^{2}

\Rightarrow

ϕ

=

h ν - \frac{1}{2} m v^{2}

=

\frac{6.626 \times 10^{- 34} \times 3 \times 10^{8}}{4000 \times 10^{- 10}} - \frac{1}{2} \times 9 \times 10^{- 31} \times {(6 \times 10^{5})}^{2}

= 3.35

\times

10^-19 J

\Rightarrow

ϕ

=

\frac{3.35 \times 10^{- 19}}{1.6 \times 10^{- 19}}

eV

= 2.0934 eV

≃

2.1 eV

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