1.

The star recedes from the earth at the speed a 100 kms^(-1) Find the doppler shift of spectrur line 3xx 10^(8)ms^(-1) ms having wavelength 5700Å

Answer»

`0.63Å`
`1.90Å`
`3.80Å`
`5.70Å`

Solution :As per Dopper effect,
`(Deltaf)/(FS)=(v_(s))/(c) ....(1) and f=(c)/(lambda)`
Taking derivative w.r.t. `lambda`
PUTTING `Deltaf=(-c)/(lambda^(2))Delta and f_(s)=(c)/(lambda)`
`:.` From equation (1)
`(c)/(lambda^(2)xx(c)/(lambda)) delta lambda=(v_(s))/(c)`
`:. delta lambda=(v_(s))/(c)xxlambda`
`=(100xx10^(3)xx 5.7xx10^(-7))/(3XX10^(8))`
`=1.90Å`


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