Question

As an admirer of Thomas Young, you perform a double-slit experiment in his honor. You set your slits 1.15 mm apart and position your screen 3.67 m from the slits. Although Young had to struggle to achieve a monochromatic light beam of sufficient intensity, you simply turn on a laser with a wavelength of 641 nm . How far on the screen are the first bright fringe and the second dark fringe from the central bright fringe? Express your answers in millimeters.

Answer 1

In Young's double slit experiment,

Condition for bright fringes

Condition for dark fringes

Given that, Distance between the slits

Distance of screen from the grating

Wavelength of light

Distance from central bright fringe to first bright fringe is ,

For small angles

Hence

For first bright fringe ,

Distance from central bright fringe to first bright fringe is

Distance from central bright fringe to second dark fringe is ,

For small angles

Hence

For second dark fringe ,

Distance from central bright fringe to second dark fringe is