de-Broglie proposed dual natrue for elecrton by putting his famous equation ` lambda = ( lambda) /( mu)`, Later on Heisenberg proposed uncertiainty principle as . `Deltap.Deltaxle(h)/(2)(h=(h)/(2pi))` . On the contray particel natrue of electron wa estabilshed on the basis fo photoelectric effect . When a photon strikes the metal suface it given up its energy to the electro . Part of this enrgy ( say W) is used by the electrons to escpe form the metal and the remaining imparts he kinetc enrgy `(1//2 mu^2)` to photoeleton . The potential applied on the surface to reduce the velocity fo photoelecton to zero is known as stoppong potential
The binding eenrgy fo electron in a metal is ` 250 kJ mol^(-1)` . The threshold frequency of metal is :

Options

A. ` 6 xx 10^(-12) sec^(-1)`
B. ` 6 xx 10^(-14) sec^(-1)`
C. ` 6 xx 10^(-10) sec^(-1)`
D. ` 6 xx 10^(-12) sec^(-1)`

Answer

B

Explanation

` hr_(0) = 250 xx 10^3 J //mol e` ltbgt `R = ( 250 xx 10^3)/( 6.023xx 10^(23))` J/molecule
` :. R_0 = ( 250 xx 10^3)/( 6.626 xx 10^(-34) xx 6.023 xx 10^(23))` ltbRgt ` = 6 xx 10^(14) sec^(-1)`.