(11C) Thin Lens Analysis
10-21-2018, 08:26 PM
Post: #1 Eddie W. Shore Senior Member Posts: 1,246 Joined: Dec 2013
(11C) Thin Lens Analysis
Given the distance from the object to the lens (U) and the focal distance (F), the program calculates object from the image from the lens (V) and magnification (M) of the image by the following equations:

V = 1 / (1/F - 1/U)
M = -V / U

HP 11C Program: Thin Lens Analysis

Note: The keystrokes are also applicable for any HP 11C emulator apps.
Code:

001 42, 21, 13  LBL C
002 15   1/x
003 34   x<>y
004 15   1/x
005 43, 36  LAST x
006 33   R↓
007 30   -
008 15   1/x
009 31   R/s
010 36   ENTER
011 16   CHS
012 43, 33  R↑
013 10   ÷
014 43, 32  RTN
To run: enter U (object distance) then F (focal distance). Then run label C ([ f ] [10^x] (C)). The first result is V (image distance). Press [R/S] to get M (magnification).

Example 1:
Input: U = 0.24 ft, F = 0.16 ft
Output: V = 0.4800 ft (R/S) M = -2.0000

Example 2:
Input: U = 1.5 ft, F = 0.8 ft
Output: V ≈ 1.7143 ft, M ≈ -1.1429

10-23-2018, 06:20 PM
Post: #2
 Dieter Senior Member Posts: 2,397 Joined: Dec 2013
RE: (11C) Thin Lens Analysis
(10-21-2018 08:26 PM)Eddie W. Shore Wrote:  To run: enter U (object distance) then F (focal distance). Then run label C ([ f ] [10^x] (C)). The first result is V (image distance). Press [R/S] to get M (magnification).

The program keeps data (U) on the stack, and the stack may be disturbed due to user interaction while the first result is displayed. That's why I suggest removing the R/S command. This way both results, V and M, are returned at the same time in X and Y. Which makes the program safe to use.

Note: the program expects the object distance U as user input. Usually distance scales on lenses are calibrated to the sum of object and image distance (U+V) which means that, especially for larger magnifications, the results will differ.

Dieter
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