PhysicsLAB: 2009 B6

In a classroom demonstration, a beam of coherent light of wavelength 550 nm is incident perpendicularly onto a pair of slits. Each slit has a width w of 1.2 x 10^-6 m, and the distance d between the centers of the slits is 1.8 x 10^-5 m. The class observes light and dark fringes on a screen that is a distance L of 2.2 m from the slits. Your notebook shows the following setup for the demonstration.

	(a) Calculate the frequency of the light.

	(b) Calculate the distance between two adjacent dark fringes on the screen.

The entire apparatus is now immersed in a transparent fluid having index of refraction 1.4.

	(c) What is the frequency of the light in the transparent fluid?

	(d) Does the distance between the dark fringes increase, decrease, or remain the same? Explain your reasoning.