1.

Let us assume that the current voltage graph for photoelectric tube consists of two straight lines as shown. On such a photoelectric tube, light of wavelength 310 nm is incident. The work function of the emitter plate is 2eV. The tube effectively acts as a solar cell to supply current to an external resistor R. Saturation current is 2A. At the what value of R will be the power dissipated in R maximum

Answer»

`1Omega`
`2Omega`
`1/2Omega`
`1/4Omega`

SOLUTION :`V_("emit")gt V_("collector")`
`V=-iR`
`V_("stop")=(hc)/(elamda)-(phi)/e=2v`
`i=2+V`
`I=2-iR`
`i(1+R)=2`
`i=2/(1+R)`
`P=i^(2)R=(4R)/((1+R)^(2))`
`(dP)/(DR)=0`
`4(1+R)^(2)-4Rxx2(1+R)=0`
`4+4R=8R`
`R=1Omega`


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