Examine the three photos in Fig. P. 4.41. Part

(a) Shows a single wide block of Plexiglas.

(b) Shows two narrow blocks of Plexiglas, each half as wide as the first, pressed lightly against one another.
(c) Shows the same two blocks, this time separated by a thin layer of castor oil. Describe what you see looking into the Plexiglas, in each photo, in detail. Compare (a) and (c). What can you say about castor oil and Plexiglas?

Figure P.4.41

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