C5 Lenses

1 a) Eddy uses a converging lens as a magnifying glass to view fine print on an instruction manual. Sketch a diagram to show the image formed. Label the principal axis and the focal point of the converging lens. b) State whether the image is virtual or real.

2 An object of height 2·5 cm is placed 12 cm in front of a converging lens. An image is produced 4 cm behind the lens. Using the lens formula, calculate: a) the focal length of the lens. b) the magnification of the lens. c) the height of the image.

3 Use a diagram to explain what is meant by the following terms when applied to a converging lens: focal point; focal length; principal axis; optical centre.

4 a) A converging lens has a focal length of 8·0 cm. An object of height 4·0 cm is placed 12·0 cm in front of the lens. Using the graph paper on the next page, determine by scale drawing: i) the image distance. ii) the height of the image. iii) the magnification of the lens. b) State ONE use of this type of lens.