A convex lens of diameter $8 c m$ is used to focus a parallel beam of light of wavelength $620 n m$ . Light is focused at a distance $20 c m$ , from the lens. What would be the radius of central bright fringe?

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Solution

$R = \frac{1.22 λ D}{r} = \frac{1.22 \times 620 \times 10^{- 9} \times 0.2}{4 \times 10^{- 2}}$
$= 3.8 \times 10^{- 6} m$

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A convex lens of diameter 8cm is used to focus a parallel beam of light of wavelength 620nm. Light is focused at a distance 20cm, from the lens. What would be the radius of central bright fringe?

R=1.22λDr=1.22×620×10−9×0.24×10−2=3.8×10−6m

A convex lens of diameter $8 c m$ is used to focus a parallel beam of light of wavelength $620 n m$ . Light is focused at a distance $20 c m$ , from the lens. What would be the radius of central bright fringe?

$R = \frac{1.22 λ D}{r} = \frac{1.22 \times 620 \times 10^{- 9} \times 0.2}{4 \times 10^{- 2}}$
$= 3.8 \times 10^{- 6} m$