Question

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? 

Solution

Correct option is

4.97 V

Let W be the work function of the cathode surface, and v the frequency of light falling on the surface. Then, according to Einstein’s photoelectric equation, the maximum kinetic energy Ek of the emitted electrons is given by  

        

               

where  is the wavelength of the incident light. 

If the cut-off potential is V0, then the maximum kinetic energy of the electron, . Thus  

        

        

If the wavelength of the incident light is increased from , then the change (decrease) in the stopping potential will be 

         

              

              

              .     

Here,  

                

             

        

             

        

             

             

Now, 

      

                

                 = 4.97 V.

SIMILAR QUESTIONS

Q1

The threshold wavelength of sodiam  metal is 6800the work function is:

Q2

The work function of a sulsstance is 4.0ev the longest wavelength of light that can cause photoelectron emission from this sulsstance is opprinately.

Q3

Potential energy of li2t electron is

Q4

The slope of frequency of incident light and stopping  potential for a given  surface will be.

Q5

If  is the radsies of the first orbit of hydrogen atom, then the radii of second, third and forth orbit in terms of  us.

Q6

Which of the following. Species will produe the shorte wavelength for thetransition  n = 2 to n = ?

Q7

The de- Broglie wavelength associated  with proton changes by 0.25%. if its momentum  is changed by the initial momentum was

Q8

The ratio of velocities of proton and  - particle is 4:1, then he ratio of their de-brohlie wavelength is

Q9

Cut-off wavelength for continous x – rays coming from x – rays tulie operating at 40 kv:

Q10

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?