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A long solenoid of 20 turns/ cm carries a current of 1.0 A. Radiation of wavelength lamda fall on a target placed within the solenoid. It is observed that electrons emitted move in a circle of largest radius 1 cm. Find the value of lamda. Given work function is 1 eV: |
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Answer» `1000Å` `B= mu_(0)ni` `=4PI xx10^(-7)xx20xx100xx1*0=8pixx10^(-4)T` The speed v of the ejected ELECTRON is GIVEN by `(mv^(2))/(r)=evB or v=(eBr)/(m)` Then `v=4*46xx10^(6)m//s` Now `(hc)/(lambda)=w+(1)/(2)mv^(2)` `=1eV+(1)/(2)xx9xx10^(-31)(4*46xx10^(6))^(2)` `=1*6xx10^(-19)+0*89xx10^(-19)` `rArr E=2*49xx0^(-19)` Now `lambda=(hc)/(E)` `:. lambda=(hc)/(2*49xx10^(-19))` `=(6*62xx10^(-34)xx3xx10^(8))/(2*49xx10^(-19))` or `lambda=7*675xx10^(-7)m=79757Å` |
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