During this Unit, students will conduct several Investigations that deal with how light is refracted by lenses and reflected by mirrors. As a point of reference, students begin by learning the parts and functions of the human eye, including its lens. The hand lens, a viewing device that contains a convex lens, is used to study the external structures of the human eye, providing an example of how convex lenses can be used to magnify the image of an object.
Students’ investigation of lenses and refraction then moves to the use of convex, concave and straight sided lenses which all refract light differently. The convex lens magnifies the image, the concave lens reduces the image size and the straight sided lens refracts but does not alter the image size.
A second viewing device, the compound microscope, is then introduced. The compound microscope contains four different convex lenses, one in each of the three objectives and one in the eyepiece. Students explore the different powers of magnification of each of the three objectives and how the differing powers of magnification affect the field of view of the specimen. Simple slides are viewed using the microscope, affording students the opportunity to investigate how refraction by the lenses of the microscope affects their view of the image. The ability of the microscope and the hand lens to magnify an image is compared and contrasted.
The compound microscope uses lenses to refract light from the specimen to form a viewable imager. Students combine hand lenses to model how the microscope functions to form a viewable image.
Conceptual Themes addressed in this Unit:
- Properties of Matter
- Changes and Reactions