In the diagram below, an experimenter sets up the optical bench to locate the po
ID: 1308090 • Letter: I
Question
In the diagram below, an experimenter sets up the optical bench to locate the position of an image made by different lenses by using parallax. The image locator, shown here between the target and lens, could be placed anywhere along the track in order to match the location of the image.
In the table below, the type and focal length of the lens, and the distance between the target plate and the lens are given. Determine in each case, the distance to the image from the lens (and its sign) and the location of the image locator.
Lens type Target platedistance (mm) Image
distance (mm) Locator
position 50 mm
concave 25 ---Select--- Between eye and lens Between lens and target Behind target 50 mm
convex 75 ---Select--- Between eye and lens Between lens and target Behind target 150 mm
convex 75 ---Select--- Between eye and lens Between lens and target Behind target
Explanation / Answer
1/S + 1/S' = 1/F
S' = (S*F)/(S-F)
1) S' = (25*-50)/(25+50) = ?16.7 .................. Between lens and target
2) S' = (75*50)/(75-50) = 150 .................. Between eye and lens
3 ) S' = (75*150)/(75-150) = -150 .................. Behind target