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A silver sphere of radius 1 cm and work function 4.7 eV is suspended from an insulating thread in free-space. It is under continuous illumination of 200 nm wavelength electromagnetic waves. As photoelectrons are emitted, the sphere gets charged and acquires a potential. The maximum number of photoelectrons emitted from the sphere is A × 10 Z (where 1 < A < 10 ). The value of Z is

Correct answer

7

Step-by-step solution

Photo emission will stop when potential on silver sphere becomes equal to the stopping potential. Stopping potential = hc &#955; - w = 6.2 - 4.7 = 1.5 &#160; eV V = Kq r = 1 . 5 = K &#215; n &#215; e r &#8658;&#160;&#160;&#160; n = 1 . 5 &#215; 1 0 - 2 1 . 6 &#215; 1 0 - 1 9 &#215; 9 &#215; 1 0 9 = 1 . 0 5 &#215; 1 0 7 &#8658; z = 7 Therefore answer is 7 .

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