19_Ch 25 College Physics ProblemCH25 Optical Instruments

19_Ch 25 College Physics ProblemCH25 Optical Instruments -...

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Optical Instruments 355 25.39 If just resolved, the angular separation of the objects is min 1.22 D λ θθ == and () 9 7 500 10 m 8.0 10 km 1.22 9.8 km 5.00 m sr θ   × == × =     25.40 The resolving power of a diffraction grating is RN m (a) The number of lines the grating must have to resolve the H α line in the first order is 3 656.2 nm 3.6 10 lines 10 . 1 8 n m R N m = = × (b) In the second order ( ) 2 m = , 3 656.2 nm 1.8 2 2 0.18 nm R N = × 25.41 The grating spacing is 4 1 cm 1.67 10 cm 1.67 10 m 6 000 d × = × 6 , and the highest order of 600 nm light that can be observed is ( )( ) 6 max 9 1.67 10 m 1 sin90 2.78 2 orders 600 10 m d m × ° = × The total number of slits is ( ) ( ) 4 10 15.0 cm 6 000 slits cm 9.00 = N , and the resolving
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