Answer to Question #161744 in General Chemistry for simran

Question

When lithium metal is irradiated with light with λ = 300 nm a stopping potential of 1.83 V is observed. Calculate the threshold frequency and work function for lithium.

Answer 1

Potential = 1.83 V

for one electronic charge

one coulomb×electronic charge

Potential = 1.83eV

E = $\frac{hc}{\lambda}$

E = $\frac{6.626×10^-³⁴ × (3×10⁸)}{300×10^-⁹}$

E = 6.626×10^-19

Now , hv = (6.626×10^-19)/( 1.6×10^-19 )

hv = 4.141

E = 4 141-1.83 = 2.311 eV

Now in Joule

E = 2.311×1.6 × 10^-19

E = 3.6976 × 10^-19

Now threshold frequency

$\nu$ =E/h = (3.6976×10^-19)/(6.626×10^-34)

$\nu$ = 55.8 × 10¹³ sec^-1