1.

A parallel beam of light of wavelength 500nm falls on a narrow slit and resulting diffraction pattern is observed on a screen 1m away. It is observed that the first minimum is at a distance of 2.5 mm from the centre of the screen. Find the width of the slit.

Answer»

Solution :The distance of the `N^(TH)` minimum from the centre of the screen is,
`x_(n)=(nDlambda)/(a)`,
where, `D=` distance of SLIT from screen,
`lambda=` wavelength of the LIGHT,
`a=` width of the slit.
`n=1` (For first minimum)
Thus, `2.5xx10^(-3)=(1xx1(500xx10^(-9)))/(a)`
`impliesa=2xx10^(-4)m`
`=0.2mm`


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