The Maximum Kinetic Energy Of Photoelectrons Emitted From A Certain Metallic Surface Is 30 EV When Monochromatic Radiation Of Wavelength  falls On It. When The Sane Surface Is Illuminated With Light Of wavelength , The Maximum Kinetic Energy Of Photoelectrons Is Observed To Be 10 EV. Calculate The Wavelength  and Determine The Maximum Wavelength Of Incident Radiation For Which Photoelectrons Can Be Emitted By This Surface. 

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Question

The maximum kinetic energy of photoelectrons emitted from a certain metallic surface is 30 eV when monochromatic radiation of wavelength  falls on it. When the sane surface is illuminated with light of wavelength , the maximum kinetic energy of photoelectrons is observed to be 10 eV. Calculate the wavelength  and determine the maximum wavelength of incident radiation for which photoelectrons can be emitted by this surface. 

Solution

Correct option is

310.5 Å, 1242 Å

Let  be the wavelength of the incident radiation, W the work function of the surface and  the maximum kinetic energy of the emitted photoelectrons. Then   

          

When illuminated with light of wavelength , then 

          

Substituting eq. (ii) from eq. (i), we get : 

        

                

            

            = 310.5 Å. 

The energy of that photon of maximum wavelength  for which photoelectrons can be emitted will be equal to the work function of the surface. Thus 

        

                  

                

                

                 = 10 eV. 

                

                .

                 = 1242 Å.        

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Q9

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Q10

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