First slide

In YDSE one of the slits is covered with a thin transparent sheet

Question

In a double slit arrangement fringes are produced using light of wavelength $4800 Å$ . One slit is covered by a thin plate of glass of refractive index 1.4 and the other with another glass plate of same thickness but of refractive index 1.7. By doing so the central bright shifts to original fifth bright fringe from centre. Thickness of glass plate is

NA

Solution

Shift $Δx = \frac{β}{λ} (μ - 1) t$
Shift due to one plate ${Δx}_{1} = \frac{β}{λ} (μ_{1} - 1)$
Shift due to another path ${Δx}_{2} = \frac{β}{λ} (μ_{2} - 1) t$
Net shift $Δx = {Δx}_{2} - {Δx}_{1} = \frac{β}{λ} (μ_{2} - μ_{1}) t$ …(i)
Also it is given that $x = 5 β$ …(ii)
Hence $5 β = \frac{β}{λ} (μ_{1} - μ_{2}) t$
$\Rightarrow t = \frac{5 λ}{(μ_{1} - μ_{2})} = \frac{5 \times 4800 \times 10^{- 10}}{(1 .7 - 1 .4)}$
$= 8 \times 10^{- 6} m = 8 μm$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App