A beam of light consisting of two wavelengths, and , is used to obtain interference fringes in a Young's double-slit experiment.(a) Find the distance of the third bright fringe on the screen from the central maximum for wavelength .(b) What is the least distance from the central maximum where the bright fringes due to both the wavelengths coincide? The distance between the two slits is and the screen is at a distance of from the slits. 

Updated on : 2022-09-05
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The wavelength of the light is
The wavelength of seond light,
Distance between the slit and the screen is .
Distance between the slits is .

The relation between the bright fringe and the width of fringe is:

For third bright fringe,

We can consider that bright frind of and the bright fringe of wavelength coincide with each other.

therefore, the least distance from the central maximum can be obtained as:

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