Name: Planck's Quantum Theory
Uploaded: 2019-07-19
Duration: 4 min 5 s
Description: Planck made many contributions to theoretical physics, but his fame rests primarily on his role as originator of the quantum theory. Watch this video to lear...

Question

The work function of copper metal is

4 e V

. Monochromatic light of wavelength

4000 \overset{o}{A}

falls upon it. Calculate the energy of the incident photon in joule. Also, express the work function in joule. Find out the kinetic energy of the fastest electron ejected from it.

Accepted Answer

Given work function of copper= $4 eV$

Wavelength of light = $4000 ° A$

The work function is defined as the energy required to eject electrons from the metal surface without imparting any kinetic energy to them. Therefore, the minimum energy of quantum required to eject photoelectrons will be,

$ϕ_{0} = 4.0 eV \times 1.6 \times 10^{- 19} = 6.4 \times 10^{- 19} J$ or

The wave length of the corresponding light is given by $E = hν = \frac{hc}{λ} or λ = \frac{hc}{E} = \frac{6.63 \times 10^{- 19} \times 3 \times 10^{8}}{6.4 \times 10^{- 19}} = 310.7 nm$

As the given radiations have more wave length, it will be less than the work function of the metal, hence the photoemission is not possible.

The energy of the incident radiations is $E = \frac{hc}{λ} = \frac{6.62 \times 10^{- 19} \times 3 \times 10^{10}}{4000 \times 10^{10}} = 4.95 \times 10^{- 19} J$

According to the Einstein photoelectric equation, the maximum kinetic energy of the emitted photon is given by,

$E_{\max} = hν - ϕ_{0}$ , substituting , we get,

$E_{\max} = 6.4 \times 10^{- 19} - 4.95 \times 10^{- 19} = 1.45 \times 10^{- 19} J$

The work function of copper metal is $4 e V$ . Monochromatic light of wavelength $4000 \overset{o}{A}$ falls upon it. Calculate the energy of the incident photon in joule. Also, express the work function in joule. Find out the kinetic energy of the fastest electron ejected from it.

Important Questions on Photoelectric Effect

Learn and Prepare for any exam you want !

The work function of copper metal is 4 eV. Monochromatic light of wavelength 4000 Ao falls upon it. Calculate the energy of the incident photon in joule. Also, express the work function in joule. Find out the kinetic energy of the fastest electron ejected from it.

Important Questions on Photoelectric Effect

Learn and Prepare for any exam you want !

The work function of copper metal is $4 e V$ . Monochromatic light of wavelength $4000 \overset{o}{A}$ falls upon it. Calculate the energy of the incident photon in joule. Also, express the work function in joule. Find out the kinetic energy of the fastest electron ejected from it.