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.        

SIMILAR QUESTIONS

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Q2

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Q3

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Q4

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Q5

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Q6

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Q7

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Q8

Light of wavelength 400 nm is incident on the cathode of a photocell, the stopping potential recorded is 6.0 V. If the wavelength of the incident light is increased to 600 nm, what will be the new stopping potential? 

Q9

When a surface is irradiated with light of wavelength 4950 Å, a photocurrent appears which vanishes if a potential greater than 0.6 V is applied across the photo-table. When a different source of light is used, it is found that the critical retarding potential is changed to 1.1 V. Find the work function of the emitting surface and the wavelength of the second source. If the photoelectrons (after emission from the surface) are subject to a magnetic field of 10 T, what changes will be observed in the above two retarding potentials? 

Q10

A monochromatic light source of frequency v illuminates a metallic surface and ejects photoelectrons. The photoelectrons having maximum energy are just able to ionize the hydrogen atom in ground state. When the whole experiment is repeated with an incident radiation of frequency , the photoelectrons so emitted are able to excite the hydrogen atom beam which then emits a radiation of wavelength 1215Å. Find the work function of the metal and the frequency v