Question

The work function of tungsten is 4.50 eV. Calculate the speed of fastest electron ejected from tungsten surface when light whose photon energy is 5.80 eV shines on the surface.
(Ans : 676 km/s)

Answer 1

Answer: $6.8 \times 10^5 m/s$

Explanation:

The energy (E) which is incident on the surface is utilized in ejecting electron (equal to work function, W) and rest is the kinetic energy (K.E.) of the electron.

E= W+K.E.

It is given that the work function of tungsten is W=4.50 eV

The energy of the incident photon is E=5.80 eV

we need find the speed of the fastest electron.

K.E. = 0.5 mv²= E-W =5.80 eV - 4.50 eV = 1.30 eV × 1.602 ×10^(-19) J/eV = 2.08 ×10^(-19) J

The mass of the electron, $m=9.1\times 10^{-31}kg$

$\Rightarrow v^2=\frac{2.08 \times 10^{-19} J}{0.5 \times 9.1\times 10^{-31}kg} = 0.46 \times 10^{12} m^2/s^2 \Rightarrow v=6.8 \times 10^5 m/s$

Answer 2

Answer:

Answer will not verified so we can not sure if it was a right answer. please can't written.