Question

In a two-slit experiment using laser light, the distance between the slits and the screen is 1.10m, and the distance between the slits is 0.040mm. If the second order (m=2) bright fringe is measured to be 4.20cm from the centerline on the screen, what is the wavelength of light?

a) 200nm b) 381nm c) 401nm d) 620nm e) 763nm

thank you in advance!

Answer 1

Solution,

For a double-slit experiment,

The bright fringes occur at,

dSin = m

Where, Using small angle approximation,

Sin Tan y/D

So, the formula changes to,

dy/D = m

Rearranging the terms,

= dy/mD

= 0.04*10^-3*4.20*10^-2/2*1.10

= 7.636*10^-7 m

= 763 nm.

Option: E

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