Question

when electromagnetic radiation of wavelength of 310 nm fall on the surface of a sodium , the electrons are emitted with K.E = 1.5 ev .calculate the work function of sodium in terms of e.v ​

Answer 1

• The work function of sodium = 2.5 ev

Solution is in attachment

The value of hc is equal to 1240 when the wavelength is in nanometres but when the wavelength is in Angstrom the value of hc = 12400

Generally the value of h = 6.626 × 10^ -34 J Hz-1

And c is speed of light

The value of hc is derived from it .

Answer 2

$\huge{\underline{\underline{\bf{ SoLuTiOn\: - }}}}♡$

°°° Explanation °°°

The correct option is A 2.5 eV

Using Einstein's Photoelectric Equation, 

KEmax = E−Wo

Given :KEmax = 1.5 eVλ = 310 nm = 3100 oA

Again,

E(eV)=12400λ(A0)=124003100=4 eV

Hence from Einstein's Photoelectric equation,

Wo = (4−1.5) eV=2.5 eV