REFLECTED-LIGHT MICROSCOPY 



139 



MenzeVs method 



Menzel substitutes Schmaltz's slit for a special transparent plate 

 (Fig. 4.15) which consists of a series of plates each of which gives 

 rise to a njl phase-shift (half-wave path difference) in relation to the 



Fig. 4.15. Menzel's method. 



ne.xt ones. A ray, such as (I), lags one-half wave-length in relation 

 to a ray such as (2). The plate is set in the vertical illuminator so 

 that it is not imaged on the object but some distance away from it. 



Fig. 4.16. Observation of cleavage planes of mica (courtesy of Prof. Menzel). 



The microscope layout is the same as the one shown in Fig. 4.13. 

 Therefore, when focusing the object the Menzel plate is out of focus. 

 Investigation of finite-distance diffraction phenomena (Fresnel's phe- 



