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 .
With what velocity must an electon travel so that its momentum is equal to that of photon fo wavelength of ` lambda = 5200Å` ?

Options

A. ` 800 ms^(-1)`
B. ` 1400ms^(-1)`
C. ` 400 ms^(-1)`
D. ` 200ms^(-1)`

Answer

B

Explanation

Momentum ` mu=`
Momentum fo wavelength ` 5200Å`
` 9. 108xx 10^(-31 ) xx u = ( 6.62 xx 10^(34))/( 5200xx 10^(-10)) (mu = h/( lambda))`
` :. 4 = 1400 m sec^(-1)`.