1.

Radiation of wavelength 180 nm eject photoelectrons from a plate whose work function is 2.0 eV. If a uniform magnetic field of flux density 5.0xx10^(-5)T is applied parallel to plate, what should be the radius of the path followed by electrons ejected normally from the plate with maximum energy:

Answer»

0.074 m
0.592 m
0. 419 m
0. 144 m

Solution :`E=hv-w=(hc)/(lambda)-w`
Here `, lambda=180 nm=180xx10&^(-9)m`
`w=2.0eV=2.0xx1.6xx10^(-9)J`
`:.E=7.8xx10^(-19)J`
ALSO `(1)/(2)mv^(2)=E:. V= sqrt((2E)/(m))`
so `v=sqrt((2xx7.8xx10^(-19))/(9.1xx10^(-31)))=1.31xx10^(6)m//s`
Radius R in a magnetic field in INDUCTION B is given
`BEV=(mv^(2))/(r) or r=(mv)/(eB)`
Using `B=5xx10^(-5)T`
Then `r=0.149 m`


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