Refraction & Lenses Lenses A lens is a curved piece of a transparent material such as glass or plastic. A lens is similar to a mirror except light is refracted, not reflected. A lens has an optical axis which divides the lens in half. The point on the optical axis where distant light rays meet when refracted, is called the focal point. The distance from the focal point to the lens is called the focal length, f. There is a focal point on both sides of the lens. mirror lens reected refracted Convex Lenses A convex lens is thicker in the middle and tapers at the ends. A light ray is drawn from the insect’s head, parallel to the optical axis. It is refracted when it meets the lens and continues through the focal point. Another light ray is drawn from the insect’s head through the focal point and is refracted by the lens. The light continues outward, parallel to the optical axis. The two rays meet at a point and form an image. The image is upside down. When the object is beyond the focal point, the image is always real and upside down. real image object (greater than 1 focal length from lens) optical axis optical axis focal point focal point virtual image object focal point focal point (less than 1 focal length from lens) concave lens focal point focal point object virtual image optical axis If you move the object closer to the lens, between the focal point and lens, the image will be virtual and upright. Concave Lenses Concave lenses are thinner at the center than at the edges. A concave lens can only produce virtual images because light passing through the lens will bend away from the optical axis. The image of the insect through the concave lens is virtual and upright. It will seem to appear on the same side of the lens as the object. convex lens concave lens © Copyright NewPath Learning. All Rights Reserved. 94-4482 Visit www.newpathlearning.com for Online Learning Resources.
Fill in the chart below with real, virtual or both. Type of lens Type of image concave convex Complete the ray diagram. Choose the correct terms from the following list: concave lens, convex lens, focal point, optical axis, real image. object © Copyright NewPath Learning. All Rights Reserved. 94-4482 Visit www.newpathlearning.com for Online Learning Resources. Refraction & Lenses Pause and Review Fill in the chart below with real, virtual or both.