Two flat glass plates are in contact along one end and are separated by a sheet of tissue paper at the other end.A monochromatic source of wavelength 509 nm illuminates the top plate.If 11 dark bands are counted across the top plate,what is the paper thickness? (1 nm = 10−⁹ m) A) 5.1 × 10−⁶ m B) 2.0 × 10−⁶ m C) 2.5 × 10−⁶ m D) 3.1 × 10−⁶ m E) 1.5 × 10−⁶ m

Question

Quizplus · Accepted Answer

The thickness of the paper can be calculated using the formula for the thickness of a wedge-shaped film: $ t = \frac{m \lambda}{2} $, where $ m $ is the number of dark bands minus one (10 in this case), and $ \lambda $ is the wavelength of light. Thus, $ t = \frac{10 \times 509 \times 10^{-9}}{2} = 2.545 \times 10^{-6} $ m, which rounds to $ 2.5 \times 10^{-6} $ m.

Two Flat Glass Plates Are in Contact Along One End