AP EAMCET Engineering 23 Apr 2019 Shift 1 Paper

The expression for work function for Li is,
v0=

W0

h

Here, the threshold frequency is given as v0 and the work function is W0
Substitute the given value in above expression.
v0=

2.42×1.602×10−19J

6.626×10−34Js

=0.584×1015s−1
The expression for work function for K is,
v0=

W0

h

Substitute the given value in above expression.
v0=

2.25×1.602×10−19J

6.626×10−34Js

=0.54×1015s−1
The expression for work function for Mg is,
v0=

W0

h

Substitute the given value in above expression.
v0=

3.70×1.602×10−19J

6.626×10−34Js

=0.89×1015s−1
The expression for work function for Ag is,
v0=

W0

h

Substitute the given value in above expression.
v0=

4.30×1.602×10−19J

6.626×10−34Js

=1.03×1015s−1
The expression for work function for Cu is,
v0=

W0

h

Substitute the given value in above expression.
v0=

4.80×1.602×10−19J

6.626×10−34Js

=1.16×1015s−1
The frequency of light is given as,
v=

c

λ

=

3×108

540×10−9

=0.56×1015s−1
The condition at which the photoelectric effect is shown is v>v0, which is only observed in case of Potassium.