1.

Lights of two different frequencies, whose photons have energies 1 eV and 2.5 eV respectively, successively illuminate a metal whose work function is 0.5 eV. The ratio of the maximum speeds of the emitted electrons will be

Answer»

`1:5`
`1:2`
`1:4`
`1:1`

Solution :Using `E=(1)/(2) mv^(2)=hv_(0)-phi`, we GET
Thus, `E_(1)=(1-0.5)=0.5eV and`
`E_(2)=(2.5-0.5)`
`=2EV`
`:.(E_(1))/(E_(2))=(v_(1)^(2))/(v_(2)^(2))=(0.5)/(2)=(1)/(4) or (v_(1))/(v_(2))=(1)/(2)`


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