In a Young’s double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is :
1.56 mm
7.8 mm
9.75 mm
15.6 mm
As we learnt in
Young Double Slit Experiment -
- wherein
Distance of a point on screen from central maxima
Path difference at that point
Ref y be the distance from the central maximum to the point where the bright fringes due to both the wavelength coincides
For , ,
for ,
i.e. with respect to central maximum 4th bright fringe of coincides with 5th bright fringe of
or y = 7.8 mm
Correct option is 2.
Option 1)
1.56 mm
This is an incorrect option.
Option 2)
7.8 mm
This is the correct option.
Option 3)
9.75 mm
This is an incorrect option.
Option 4)
15.6 mm
This is an incorrect option.
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