Chapter 5: Q20E (page 1212)
Diffraction and Interference Combined. Consider the interference pattern produced by two parallel slits of width and separation d, in which d =3 a. The slits are illuminated by normally incident light of wavelength . (a) First, we ignore diffraction effects due to the slit width. At what angles from the central maximum will the next four maxima in the two slit interference pattern occurs? Your answer will be in terms ofd and . (b) Now we include the effects of diffraction. If the intensity at is , what is the intensity at each of the angles in part (a)? (c) Which double-slit interference maxima are missing in the pattern? (d) Compare your results to those illustrated in Fig. 36.12 c. In what ways are your results different?
Short Answer
(a) The angles are
(b) The intensity at each of the angles is
(c) The third interference maxima is missing in the pattern.
(d) Fourth interference is always dark, while in this case, the third interference is the missing one.