Question

A 620 nm light falls on a photoelectric surface and electrons with the maximum kinetic energy of 0.14 eV are emitted. (a) Determine the work function (in eV). eV (b) Determine the cutoff frequency of the surface (in THz). THz (c) What is the stopping potential (in V) when the surface is illuminated with light of wavelength 420 nm

Answer 1

To determine the work function of the photoelectric surface, use the equation for the energy of a photon and subtract the maximum kinetic energy of electrons. Use the cutoff frequency equation to find the cutoff frequency of the surface. Use the stopping potential equation to determine the stopping potential when the surface is illuminated with light of a different wavelength.

Step-by-step explanation:

To determine the work function of the photoelectric surface, we can use the equation:

Energy of a photon = Work function + Maximum kinetic energy of electrons

The energy of a photon is given by the equation:

Energy of a photon = (Planck's constant * speed of light) / wavelength

By substituting the values given (wavelength = 620 nm), we can calculate the energy of the photon. Subtracting the maximum kinetic energy of electrons (0.14 eV) from the energy of the photon will give us the work function in eV.

To determine the cutoff frequency of the surface, we can use the equation:

Cutoff frequency = (speed of light) / (wavelength)

By substituting the values given (wavelength = 620 nm), we can calculate the cutoff frequency in THz.

To find the stopping potential when the surface is illuminated with light of wavelength 420 nm, we need to use the equation:

Stopping potential = (Energy of a photon - Work function) / charge of an electron

By substituting the values given (wavelength = 420 nm), we can calculate the stopping potential in volts.

Answer 2

(a) The work function is 1.86 eV.

(b) The cut off frequency is 450 THz.

(c) The stopping potential is 1.16 V.

Step-by-step explanation:

incident wavelength = 620 nm

Kinetic energy, K = 0.14 eV

According to the photoelectric equation

E = W + KE

where, W is the work function, KE is the kinetic energy.

(a) Let the work function is W.

`W = E - KE\\W = (h c)/(\lambda )- KE\\W =(6.63* 10^(-34)*3* 10^(8))/(620* 10^(-9)* 1.6* 10^(-19))-0.14\\\\W =1.86 eV`

(b) Let the cut off frequency is f.

W = h f

`1.86* 1.6* 10^(-19) = 6.63* 10^(-34)* f\\f = 4.5* 10^(14) Hz =450 THz`

(c) Let the stopping potential is V.

`E = W + eV\\(6.63* 10^(-34)* 3* 10^(8))/(420* 10^(-9)* 1.6* 10^(-19))=1.8 + eV\\\\V = 1.16 V`