Notes

Outline

Technical Physics 2 Chapter 27 Lenses

Converging A converging lens refracts light in such a way that parallel light rays are brought to a focal point beyond the lens

Diverging A diverging lens refracts light in such a way that parallel light rays will be spread out but appear to have come from a focal point before the lens

Ray tracing 3 principle rays In parallel to the axis of symmetry, refracted through the focal point #2 of a converging lens or appears to have come from focal point #1 of a diverging lens In through the focal point #1of a converging lens or follows a path toward focal point #2 of a diverging lens, refracted parallel to the axis of symmetry In through the center of the lens, is not bent

Ray Tracing (Converging) Real images are always on the opposite side from the object. The focal length is considered positive.

Ray Tracing (Diverging) Images of real objects formed by diverging lenses are always virtual, upright and smaller in size. The focal length is considered negative.

Calculations Lens equation Magnification

Keys to problem solving Make a sketch to estimate the size and location of the image. Also determine the nature ; is it real or virtual, and is it upright or inverted. Calculations should verify the nature real images Þ q is a positive value virtual images Þ q is a negative value upright images Þ y’ is a positive value inverted images Þ y’ is a negative value

Other observations The Eye Lens combinations Microscope telescope Lens Defects spherical aberration chromatic aberration

The Human Eye Accomodation http://users.erols.com/renau/eye_applet.html Near sightedness Far sightedness Astigmatism Magnification