The work functions of cesium (Cs) and lithium (Li) metals are 1.9 eV and 2.5 eV, respectively. If we incident a light of wavelength 550 nm on these two metal surfaces, then photo-electric effect is possible for the case of

Question

For light of wavelength 550 nm, incident energy:

E

=

1240

e

V

.

n

m

550

n

m

=

2.25

e

V

E = \frac{1240\ eV.nm}{550	ext{\ }nm} = 2.25\ eV

For photoelectric effect

E

>

ϕ

E > \phi

Given

ϕ

c

s

=

1.9

e

V

a

n

d

ϕ

L

i

=

2.5

e

V

\phi_{cs} = 1.9\ eV\ and\ \phi_{Li} = 2.5\ eV

Thus photoelectric emission is possible for cesium and Not for lithium

PYQ · Accepted Answer

C