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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