A Very Fine Thread Is Placed Between Two Glass Plates

question 12

Multiple Choice

A very fine thread is placed between two glass plates on one side and the other side is touching to form a wedge. A beam of monochromatic light of wavelength 600 nm illuminates the wedge and 178 bright fringes are observed. What is the thickness of the thread?

• A) 22.3 μm
• B) 26.7 μm
• C) 32.3 μm
• D) 53.3 μm
• E) 76.3 μm