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Light of wavelength 2475 Å is incident o...

Light of wavelength `2475 Å` is incident on barium. Photoelectrons emitted describe a circle of radius `100 cm` by a magnetic field of flux density `(1)/(sqrt(17)) xx 10^(-5) Tesla`.
Work function of the barium is (Given `(e )/(m) = 1.7 xx 10^(11)`)

A

`1.8eV`

B

`2.1 eV`

C

`4.5 eV`

D

`3.3 eV`

Text Solution

Verified by Experts

The correct Answer is:
C
r (Radius) = `(sqrt(2mk))/(qB)`
`implies k = (q^2B^2r^2)/(2m) =(e/m)(eB^2r^2)/2`
`implies k =1/2 xx1.7 xx10^(11) xx1.6 xx10^(-19) xx[1/sqrt(17)xx10^(-5)]^(2)xx(1)^2`
`= 8 xx10^(-20) J = 0.5 eV`
`k_("max") = E-phi_0`
`impliesphi_0=((12375)/(2475))eV-0.5 eV = 4.5 eV`
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