Geometrical optics / by Archibald Stanley Percival.

  • Percival, A. S. (Archibald Stanley), 1862-
Date:
1913
Catalogue details

Licence: In copyright

Credit: Geometrical optics / by Archibald Stanley Percival. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    the second nodal point. A warning must be given when dealing with menisci, as the point 0 must always be con- sidered as situated in the glass, even when it is not, as in Fig. 37, or totally erroneous results will be obtained. Con* sequently the method must be regarded simply as a trick or device by which it can be mathematically proved that accu- rate results will be obtained. We will take the case of Fig. 38 as an example, where n = 3, r2 = — 4, t = 2, and OA and OB we have found to be — f and f respectively. We are now considering the left- hand surface to be the incident surface A, so that light is supposed to be travelling from Q to P. The problem is the same as that on p. 57; we first find the image of 0 formed by the surface A. As 0 is in the glass, fx0 = 1*5 and fi = 1, so— // = J^=^±l*| = 9, while/, = =£fi> -=|- -6 JL fi - fio 1-1-5 ' no I'o ••KAOr?-J)_/1'- -f-9 -69 23 Similarly for the surface B— _ -fMirs _ -l-5(-4)_ 6 19 h ~7^7To~ i-i-5 -0-5- 1Z> and /3» = -£/2'=g = 8 And as OB or p' = f KB or a* - J£- - A* 8 = 64 = L6 K * 01 q ~p' -/2' ~| + 12 92 23 The position of the nodal points is quite independent of the direction in which the light is travelling; it is only their names (first or second) that are changed. We have been considering light passing from Q to P, so K' refers to the left-hand surface. In the diagram the reverse condition is indicated; the light is passing from P to Q, so that the right-hand surface is the incident surface, and the nodal