question_answer

Two rectangular glass plates are in contact at one edge while the other edges are separated by a space of some suitable thickness so as to form a low angle wedge. The spacer is placed parallel to the line of contact and is at a distance of 10 cm from it. When viewed normally in light of wavelength 5500 A, a series of evenly spaced dark bands 0.5 mm apart are seen. The thickness of the spacer is :   

A) 0.0425cm

B) 0.0036cm

C) 0.0055cm

D) 0.0254cm

Correct Answer: C

Solution :

[c] \[\beta =\frac{\lambda }{2\mu \alpha }=\frac{\lambda }{2\mu \left( \frac{t}{x} \right)}\] \[=\frac{\lambda x}{2\mu t}\]  or \[t=\frac{\lambda x}{2\beta \mu }\]