Using a homemade optics bench, the focal length of a convex lens was determined. The object used was a candle flame.The candle was movable along the meter stick. The object was placed at different lengths from the lens, all factors of the focal length, and the image described as seen on the screen. The images were compared to those which were seen theoretically by sketching the ray diagrams earlier. The same procedure was performed using diverging lens. The optics used in a camera was drawn utilizing the information from the lens demonstration.

Ray diagrams were drawn by Abby. One had the object placed between the focal length and twice the focal length, and the second had the object placed at the focal length. The incident rays and refracted rays were drawn to scale on graph paper, and the images of each described. The lens set was then used to show the convergence of light rays as they passed through convex lenses of different thickness. The thicker the lens, the shorter the focal length of the lens. The divergence of light using a concave lens was demonstrated using the lens set and a laser light source. The images formed were seen to be present in front of the lens, formed by virtual light rays.

Using the convex lens as the example, the main parts of the lens and image formation were sketched and defined. This included the center of the lens, the principal axis, the focal plane, the focal point, the focal distance and twice the focal distance. Rules governing the refraction of light through a lens were reiterated as well as the method used to determine where and how large an image is. Two ray diagrams were sketched, one with the object placed greater than 2f and one with the object placed at 2f. The type of image was explained by the student, eg: inverted or upright, size in relationship to object, same, larger or smaller, type, real or virtual. Each ray diagram was drawn on a separate graph paper.

How light reacts as it passes from air to glass was used to describe the way in which a lens reacts to light. Using a series of 4 large lens types, the names of each type was elicited from their shape. The definition of a lens was derived from the physical appearance of the lens and how it responded to light.

examples of lenses which lead to the definition of lenses. Examples which demonstrate the 2 main types of lenses, convex and concave. Using the lens kit and lasers, showing how a convex lens is actually 2 prisms placed base to base, while a concave lens behaves like 2 prisms placed apex to apex. Tracing incident rays through a convex lens demonstrates that they all refract to a point, making a convex lens a converging lens. The same is done for a concave lens, demonstrating the dispersing or spreading of the refracted rays, making a concave lens a divergent lens.

See earlier outline for today

The definition of a lens, the defined parts of a lens which will function in image formation. These will include the focal point, the focal length, the focal plane, the principal axis, and the center of the lens. Convex and concave lenses defined in terms of shape and convergence or divergence of light. All demonstrated using the large lens exhibit and laser light beams.

Specific questions taken from the end of the chapter were used to review and evaluate the degree of learning for this unit. The questions involved concepts, mathematical calculations, and diagram evaluation. Each question was followed with a discussion of the answer, and why/how it was arrived at.

Same outline as listed for Wednesday- chapter question review

A review of basic terms was needed to insure a smooth transition from reflection and refraction into curved mirror images.The types of curved mirrors was presented, with the convex mirror used to demonstrate the important parts, such as the principal axis, the center of the mirror surface, the radius of the mirror,and the focal point.