8. The spherical waves of wavelength \(\lambda\) emitted from a single point source are passing through two small holes, S\(_1\) and S\(_2\), which are separated by the distance of a, as shown in the figure. If c ＞＞ a, what is the approximated condition for destructive interference at a point P on the screen? (A)\(a\sin\theta = n\lambda\) (B)\(a\sin\theta = (n + \frac{1}{2})\lambda\) (C)\(a\sin\theta = \frac{n\lambda}{2}\) (D)\(2a\sin\theta = n\lambda\) (E)None of the above

9. A laser beam of wavelength \(\lambda\) shined on a spectrometer with the grating spacing a is split into two beams of wavelengths \(\lambda_1\) and \(\lambda_2\) due to the 2nd order diffraction. If \(\lambda_2\) is slightly longer than \(\lambda_1\) and \(\theta\) is the diffraction angle for \(\lambda_1\), what is the difference in diffraction angles of the two beams? (A)\(\frac{\lambda_2 - \lambda_1}{2a\cos\theta}\) (B)\(\frac{\lambda_2 - \lambda_1}{a\cos\theta}\) (C)\(\frac{2(\lambda_2 - \lambda_1)}{a\cos\theta}\) (D)\(\frac{\lambda_2 - \lambda_1}{a\sin\theta}\) (E)None of the above

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