Lenses

1. Lenses P3.1.5

2. Objectives • Describe a converging lens/diverging lens. • Explain the difference between the “real” image and the “virtual” image. • Design and construct a pinhole camera.

3. Key words • Concave • Convex • Converging • diverging • Lenses • Real image • Virtual image • magnification

4. Starter activity • Produce a spider diagram of 10 items which use lenses.

5. Investigation • Using a ray box, investigate the behavior of light rays when it passes through converging (convex) and Diverging (Concave) lenses. • Draw a diagram and explain what is happening.

6. Types of lenses

7. Pinhole camera • http://www.exploratorium.edu/science_explorer/pringles_pinhole.html Are the images you see with the camera inverted or upright? Why?

8. Image magnification The magnification produced Image height By a lens = Object height

9. Task • A postage stamp is inspected using a magnifying glass with a converging lens. • Draw a diagram to show what you would expect to see.

10. P3 2.5 Using lenses • Draw a ray diagram showing the operation of a camera. • Describe the image formed when a convex lens is used as a camera or as a magnifying glass

11. Position of film or array of pixels on a CCD Converging lens F F Draw a ray diagram to show that a real, inverted and magnified image is produced if the object is between f and 2f from the lens. When light falls on R G B pixels a voltage is produced and stored in a memory .

12. This could be a projector lens Magnified ! As an object approaches a camera should the lens be moved away from the sensor or towards the sensor/film?

13. This could be a projector lens Magnified ! As an object approaches a camera should the lens be moved away from the sensor or towards the sensor/film?

14. This could be a magnifying glass This could be a torch lens instead of using a mirror

15. This could be a magnifying glass This could be a torch lens instead of using a mirror