A fine hair is trapped between two microscope slides, forming an air wedge. With normally incident light of wavelength 550 nm, the hair is at the fifth dark band counting from the common edge. Find the hair diameter in nm.

Question

G1 Physics · Accepted Answer

For an air wedge in reflected light, dark fringes satisfy 2t=mλ. At the fifth dark band counting the contact dark as m=0, m=4. Thus t=4λ/2=2λ=1100 nm.