1.

If the distance between the first maxima and fifth minima of a double-slit pattern is 7 mm and the slits are separated by 0.15 mm with the screen 50 cm from the slits, then wavelength of the light used isA. 600 nmB. 525 nmC. 467 nmD. 420 nm

Answer» Correct Answer - A
For minima `y_(n)=(2n-1)(lamdaD)/(2d)`
where n is the no. of minimum
For maxima `y_(n)=(nlamdaD)/(d)`
`y_(5^(th)"dard")=(9lamdaD)/(2d):y_(1^(@)" maxima")=(lamdaD)/(d)`
By equation `y_(5^(@)" min")-y_(1^(@)" max")=7xx10^(-3)`
`(9lamdaD)/(2d)-(lamdaD)/(2d)=7xx10^(-3)implieslamda=(7xx10^(-3)xx15xx10^(-5)xx2)/(7xx50xx10^(-2))`
`thereforelamda=600nm`


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