A laser of wavelength 650 nm illuminates a pair of identical narrow slits separated by 0.40 mm. A viewing screen is placed 2.5 m from the slits and the familiar interference pattern of bright and dark regions appears.
Answer the following questions about how the pattern would change under different conditions.
(a) Describe qualitatively how the spacing between adjacent bright regions on the screen would change if the slit separation were reduced to 0.20 mm while all other quantities remained the same.
(b) Explain, with reference to the geometry of the setup, why using the approximation that the angle to a bright region equals the tangent of that angle is reasonable for the first three bright regions in the original experiment.