Part 1 Light of wavelength 3.0 × 10?7 m shines on the metals lithium, iron, and
ID: 1730985 • Letter: P
Question
Part 1
Light of wavelength 3.0 × 10?7 m shines on the metals lithium, iron, and mercury, which have work functions of 2.3 eV, 3.9 eV, and 4.5 eV, respectively. Which of these metals will exhibit the photoelectric effect? The speed of light is 3 × 108 m/s and Planck’s constant is 6.63 × 10?34 J · s.
1. lithium
2. None of these
3. lithium and iron
4. mercury
5. iron and mercury
6. iron
Part 2
For those metals that do exhibit the photoelectric effect, what is the maximum kinetic energy of the photoelectrons?
1. 7.4 eV, 5.0 eV and 2.1 eV
2. 1.84375 eV and 0.24375 eV
3. None of these
4. 10.1 eV
5. 5.2 eV and 2.4 eV
Explanation / Answer
Energy in incident photons
E= hc/lambda= 6.36*10^-34* 3*10^8/(3*10^-7)= 4.14 eV
As the workfuction of iron and lithium is less than incident photon energy, hence iron and lithium exhibit photoelectric emmision.
Option(3) is correct.
---------
Kinetic energy of lithium electron= 4.14-2.3= 1.84375 eV
Kinetic energy of iron, = 4.14- 3.9= 0.24375 eV
Option(2) is correct.
---------
Comment in case any doubt..goodluck