Two flat glass plates are in contact along one end and are separated by a sheet of paper 3.0 *10 ^- ⁶ m thick at the other end. The top plate is illuminated by a monochromatic light source of wavelength 490 nm. How many dark parallel bands will be evident across the top plate? (1 nm = 10 ^- ⁹ m) Note that a dark band occurs where the plates contact.

Question

Quizplus · Accepted Answer

The number of dark bands is given by:$$N = \frac{2dt}{\lambda}$$where d is the thickness of the paper, t is the wavelength of the light, and N is the number of dark bands.Plugging in the given values, we get:$$N = \frac{2(3.0 	imes 10^{-6} 	ext{ m})(490 	imes 10^{-9} 	ext{ m})}{490 	imes 10^{-9} 	ext{ m}} = 13$$Therefore, the correct answer is A.

Two Flat Glass Plates Are in Contact Along One End