An experimenter needs exactly five bright interference fringes (including the central…
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics
Problem
An experimenter needs exactly five bright interference fringes (including the central maximum) to appear inside the central diffraction envelope of a double-slit pattern. The slit separation is d=0.80mm, and the apparatus is illuminated with red light of wavelength λ=650nm.
(a) Determine the maximum value of the ratio a/d that will satisfy the requirement stated above.
(b) Using the result from part (a), calculate the corresponding slit width a to the nearest micrometre.
(c) Explain qualitatively how the appearance of the pattern (number and brightness of visible fringes) would change if the actual slit width were manufactured to be slightly smaller than the value found in part (b).