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  • The two slits are apart from each other and illuminated with a light of wavelength <img a

The two slits are 1 \mathrm{~mm} apart from each other and illuminated with a light of wavelength 5 \times 10^{-7} \mathrm{~m}. If the distance of the screen is 1 \mathrm{~m} from slits, then the distance between third dark fringe and fifth bright fringe is:

Option: 1

1.5 mm


Option: 2

0.75 mm


Option: 3

1.25 mm


Option: 4

0.625 mm


Answers (1)

best_answer

Distance of \mathrm{5^{\text {th }}} bright fringe from central fringe, \mathrm{x_{5 D}=\frac{5 \lambda D}{d}}
Distance of \mathrm{3^{\text {rd }}} dark fringe from central fringe, \mathrm{x_{3 D}=\frac{(2 \times 3-1) \times D}{2 d}=\frac{5}{2} \frac{\lambda D}{d}}

Required distance, \mathrm{\mathrm{x}_{5 \mathrm{D}}-\mathrm{x}_{3 \mathrm{D}}=\left(5-\frac{5}{2}\right) \frac{\lambda \mathrm{D}}{2}=\frac{5}{2} \times \frac{5 \times 10^{-7} \times 1}{1 \times 10^{-3}}=1.25 \mathrm{~mm}}

Posted by

Ritika Kankaria

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