Question

A photocell is operating in saturation mode with photo current 4.8 new a with a monochromatic radiation of wavelength 3000 angstrom and power 1 mW is incident when another monochromatic radiation of wavelength 1650 and storm power 5 mW is incident it is observed that maximum velocity of photoelectron increases to two times. assuming efficiency photoelectron generation per incident to be same for both the cases calculate threshold wavelength for the cell. ​

Answer 1

$\Large\bold{\underline{\underline{Answer:-}}}$

$\Large\bold{\boxed{\boxed{4133 A\degree}}}$

$\rule{200}{4}$

$\bf\small\bold{\underline{\underline{Step-By-Step\:Explanation:-}}}$

$\bf\bold{K1 = \frac{12400} {3000}-W = 4.13 - W}$

$\bf\bold{K2= \frac{12400} {1650}-W = 7.51 - W}$

Since, v2 = 2v1

So, K2 = 4 K1

Solving above equation we get

W = 3 ev

Therefore, Threshold wavelength $\bf\bold{\lambda_0 = \frac{12400} {3} = 4133 A^\circ }$

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Threshold wavelength = the maximum wavelength of radiation which can produce electromagnetic effect.

Denoted by $\bf\bold{\lambda_0}$