20. A spectrometer with a grating spacing \(d_{\lambda}\) is used to separate two laser beams of wavelengths \(\lambda\) and \(\lambda + \Delta \lambda\) (\(\Delta \lambda << \lambda\)) by the 2nd order diffraction. The difference of the diffraction angles \(\Delta \theta\) is

(A)\(\frac{2\Delta\lambda}{d\cos\theta}\)
(B)\(\frac{\Delta\lambda\sin\theta}{2d}\)
(C)\(\frac{\Delta\lambda\tan\theta}{2d}\)
(D)\(\frac{4\Delta\lambda}{d\sin\theta}\)
(E)None of the above
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