Question: Two slits spaced 0.5mm apart are illuminated by monochromatic light of wavelength 650 nm.

(a) What color is this light?

(b) Using the notation of Fig. 10.10 write down the angles θ at which the first three bright fringes appear to one side of the central fringe. Express these angles in radians.

(c) Is the small-angle approximation valid for this exercise? Explain.

(d) If the interference pattern is projected onto a screen a distance D = 2m from the slits, what is the distance between the fringes?

Fig. - (a) Cylindrical wavefronts emerge from two slits illuminated by a laser beam. The lines along which the points of intersection lie are where there is constructive interference. (b) By the time these wavefronts reach the distant screen , they are nearly plane waves; the places where the points of intersection strike the screen are where intensity maxima occur.