Pupil sheet · Lenses and images
Lenses and images — final check
Name ______________________ Date ____________
Work alone, with the lesson closed. Answer every question; there are no hints.
1. define / determine / describe
(a) Define the focal length of a lens. (b) Define the principal axis of a lens. (c) An object 3.0 cm tall stands on the principal axis 30 cm from a converging lens of focal length 12 cm. On paper, draw a ray diagram at half size. Determine how far from the lens the image is and how tall it is, in real centimetres. (d) Describe the image.
(c) Distance of the image from the lens (real cm): ______________ unit ________
(c) Height of the image (real cm): ______________ unit ________
(a) and (b) The definitions, and (d) the image
2. describe / state / explain / determine
(a) A ray box sends a wide parallel beam of light through a converging lens of focal length 15 cm, onto a screen 15 cm behind the lens. The lens is then swapped for a diverging lens of focal length 15 cm. Describe what the screen shows each time. (b) The diverging lens is then held a few centimetres above a page. The print seen through it looks upright and smaller. State whether a screen could show this image, and explain why. (c) Supplement. A watchmaker uses a converging lens of focal length 9.0 cm as a magnifying glass to look at a tiny screw. Explain why the lens stops working as a magnifying glass if the screw is moved further than 9.0 cm from it. (d) Supplement. The screw is 0.8 cm tall and 3.0 cm from the lens. On paper, draw a full-size ray diagram. Determine how far from the lens the image is and how tall it is. (e) Supplement. Explain why a short-sighted person needs a diverging lens.
(d) Supplement: Distance of the image from the lens: ______________ unit ________
(d) Supplement: Height of the image: ______________ unit ________
(a) The screen each time, (b) the screen and the print seen through the diverging lens, (c) Supplement: beyond 9.0 cm, and (e) Supplement: short sight