Optics
Uploaded by lioannid on Oct 09, 1999
Aim: To examine characteristics of a converging lens and the images they create. Also to examine the focal length and how the focus point may be found and developing rules for locating an image via ray drawings and the intersection of rays. Chromatic aberration will also be explored and why it happens.
Theory: Both lenses and mirrors have a principle axis, yet a lens has two focal points as opposed to a mirror that has only one. When considering converging lenses, the primary focal point (PF) can be found on the opposite side of the lens in regards to the light. The secondary focal point (SF) being on the same side as the light source. Focus points on thin double convex lenses are located at either side of the lens, measured from the middle of the lens itself (see below). Chromatic aberration is a problem of converging lenses that will also be explored in this experiment. A description of each image produced will also be given (attitude, type, magnification and location).
Apparatus: The main tools (apparatus) used in the experiment consist of a ray box containing cards which allow one, two, three or four rays onto a sheet of paper at a time so that rays path from the box to the mirror will be able to be traced. Also two (2) different types of converging lenses, one being cylindrical while the other being spherical, the difference being that the spherical one is used for viewing, the cylindrical one for use with the ray box. These lenses are one of many different sorts of lenses in the "lens box". The use of a ruler would also be helpful so that accurate measurements may be taken.
Method:
1. A cylindrical lens was placed on paper and traced around, a principal axis was drawn making sure that it's at rights angles to the lens. The ray box was switched on (exposing only one ray) and lined up parallel to the principle axis, a mark where the ray leaves the box was made as well as where it hits the lens (on both sides) and where the ray bisects the principle axis. After this, the ray box was removed and using a ruler, rays were accurately drawn. The focus point (f) was measured to be of length 7.3cm (7.25).
2. The lens was replaced back on a sheet of paper with ray box emitting three rays, the...