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In a young's double slit experiment with slit sepration 0.1mm, one observes a bright fringe at angle \frac{1}{40} rad by using light of wavelength \lambda _{1}. When the light of wavelength \lambda _{2} is used a bright fringe is seen at the same angle in the same set up. Given that \lambda _{1} and \lambda _{2} are in visible range (380nm to 740nm), their values are:

 

  • Option 1)

    625 nm, 500nm

  • Option 2)

    380 nm, 525 nm

  • Option 3)

    380 nm, 500 nm

  • Option 4)

    400 nm, 500 nm

Answers (1)

best_answer

 

Young Double Slit Experiment -

- wherein

y=\Delta x\cdot \left ( \frac{D}{d} \right )

y= Distance of a point on screen from central maxima

\Delta x= Path difference at that point

path \: \:difference = d\: \: sin\theta \approx d\times \Theta

d=0.1, \: \: \Theta =\frac{1}{40}so\: \: path\: \: difference =0.1 \times \frac{1}{40}=2500nm

for\: \: bright\: \: fringe

path\: \: difference\: \: is\: \: multiple \: of \: \lambda

for \: \lambda _{1}

2500=n\lambda _{1}

for\: \: \lambda _{2}

2500=m\lambda _{2}

\Rightarrow 2500=n\lambda _{1}=m\lambda _{2}

for\: n=4,\lambda _{1}=625nm

for \: \: m=5, \lambda _{2}=500nm

 

 

 

 


Option 1)

625 nm, 500nm

Option 2)

380 nm, 525 nm

Option 3)

380 nm, 500 nm

Option 4)

400 nm, 500 nm

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