Question

A pair of narrow slits, separated by 1.8 mm, is illuminated by a monochromatic light source. Light waves arrive at the two slits in phase, and a fringe pattern is observed on a screen 4.8 m from the slits. If there are 5.0 complete bright fringes per centimeter on the screen near the center of the pattern, what is the wavelength of the monochromatic light?

Answer 1

750 nm

Step-by-step explanation:

`d` = separation of the slits = 1.8 mm = 0.0018 m

λ = wavelength of monochromatic light

`D` = screen distance = 4.8 m

`y` = position of first bright fringe =
`(1cm)/(5 fringe) = (0.01)/(5) = 0.002 m`

`n` = order = 1

Position of first bright fringe is given as

`y = (nD\lambda )/(d)`

`0.002 = ((1)(4.8)\lambda )/(0.0018)`

λ = 7.5 x 10⁻⁷ m

λ = 750 nm