# Physics

posted by .

The work function for potassium and cesium are 2.25 and 2.14 eV, respectively.
a) Will the photoelectric effect occur for either of these elements with incident light of wavelength 565 nm?
b) With light of wavelength 518 nm ?

• Physics -

convert 565 and 518 to wavelength.

Fnergy= hc/lambda

set lambda=hc/energy

now convert eV to joules, plug it in and compute lambda cutoff for each metal. If lambda oncoming is shorter than 565, and 518nm, photoelectric effect occurs.

• Physics -

W potassium eV 0 ( ) = 2.25 ,
W caesium eV 0 ( ) = 2.14 ,
7
1 5650 10 m

λ = × ,
7
2 5180 10 m

λ = ×
34
h J s 6.63 10 .

= × ,
8
c m s = × 3 10 /
W potassium eV 0 ( ) = 2.25
19
2.25 1.6 10 J

= × ×
19
3.6 10 J

= ×
W caesium eV 0 ( ) = 2.14
19
2.14 1.6 10 J

= × ×
19
3.424 10 J

= ×
i.
34 8
7
1
6.63 10 3 10
5.650 10
hc

× × ×
=
 ×

19
3.52 10 J

= ×
This energy (of the
incident photon) is greater
than W0
(caesium), but
less than W0
(potassium).
Hence, photoelectric effect
will occur in case of
caesium, but not in case
of potassium.
ii.
34 8
7
2
6.63 10 3 10
5.180 10
hc

× × ×
=
λ ×

19
3.84 10 J

= ×
This is greater than W0
for potassium and for
caesium. Hence,
photoelectric effect will occur in both cases.

## Similar Questions

1. ### Physics -

The work function of cesium surface is 2.0eV (a)find the maximum kinetic energy of the ejected electrons when the surface is illuminated by violet light with wavelenght = 4.13 x 10^3 Angstroom unit h = 6.63 x 10^9-34)Js (b) what is …

3. ### Physics

The "work function", or the minimum energy needed to eject an electron from the metal, can be expressed in several different ways. As stated on the applet page, sodium has a work function of 2.75 eV. In class, we discussed how to determine …
4. ### Physics

Electrons are ejected from a photoelectric cell with a maximum kinetic energy of 1.20 eV. If the incident light has a wavelength of 410nm, what is the work funtion?
5. ### physics

Light falls on a photoelectric surface that has a work function of 2.90 eV. If the voltage required to stop the ejected electrons is 0.210 V, what is the wavelength of the incident radiation?
6. ### Physics

In a photoelectric-effect experiment it is observed that no current flows unless the wavelength is less than 570nm . A)What is the work function of this material?
7. ### Physics

In a photoelectric-effect experiment it is observed that no current flows unless the wavelength is less than 570nm . A)What is the work function of this material?
8. ### Physics

What is the threshold frequency for the photoelectric effect on lithium (phi= 2.93eV)?
9. ### Physics

What is the threshold frequency for the photoelectric effect on lithium (phi= 2.93eV)?
10. ### Physics

What is the threshold frequency for the photoelectric effect on lithium (phi= 2.93eV)?

More Similar Questions