1.

If the frequency of a wave is increased by `25%`, then the change in its wavelength will be: (medium not changed)A. `20%` increaseB. `20%` decreaseC. `25%` increaseD. `25%` decrease

Answer» Correct Answer - B
Since, the medium has not changed, speed of wave remains same.
`impliesv=flamda=`constant
`f_1lamda_1=f_2lamda_2`
`impliesf_1lamda_1=(1.25f_1)lamda_2` (`:.` frequency increased by `25%`)
`lamda_2=(lamda_1)/(1.25)implies_2` decreases.
`%` change in wavelength `=(lamda_1-lamda_2)/(lamda_1)xx100`
`(lamda_1-(lamda_1)/(1.25))/(lamda_1)xx100=(0.25)/(1.25)xx100=(100)/(5)=20%`


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