1. 4.6 Lenses - Real Images (p346-349)Lenses (p346-349)

2. What is a Lens? A lens is a thin, transparent piece of glass or plastic that has at least one curved side. The curved side or sides may be concave or convex. There are 2 types of lenses Converging Lens Diverging Lens

3. What Do Lenses Do? Lenses come in many sizes and shapes and are made for many purposes. a) the eye b) camera c) telescope

4. What Do Lenses Do? d) eyeglassese) magnifying glass

5. What Do Lenses Do? Lenses can change the appearance of objects, making images sometimes appear -larger or smaller than the object -upside down -distorted Lenses can focus light because of refraction. Light refracts when entering and leaving a lens. What lenses do you use in your life?

6. Converging Lenses Also called convex lenses. When parallel rays pass through a converging lens, the rays all meet at one point on the other side of the lens. This point is the focal point (F).

7. Diverging Lenses Also called concave lenses. When parallel rays pass through a diverging lens, the rays move apart. Diverging Lens

8. 1) Rays parallel to principal axis (PA) pass through F. 2) Rays through centre of the lens are not refracted. 3) Rays through F ‘ emerge parallel to principal axis. F´F´ F Object PA Image Ray Diagrams for Converging Lenses

9. Image for Converging Lenses (LOST) Recall that images have 4 key characteristics: Location Is the image distance shorter or longer than the object distance? Is the image behind or in front of the lens? Orientation Is the image oriented in the same direction as the object? Is it upright (right side up) or inverted (upside down)? Size (or Magnification ) How big is the image compared to the object? Is it larger or smaller? Type Is the image real (the rays meet) or virtual (the rays must be extended backward to meet)?

10. Copyright © 2010 McGraw-Hill Ryerson Ltd. The characteristics of the image of an object placed beyond F of a converging lens are: (L) the image is farther from the lens than the object is (O) the image is inverted (S) the image is larger than the object (T) the image is real Describe Image if Object is Beyond F (LOST)

11. So, what does that look like? Let’s Try This: Where is the Object?

12. Ray Diagrams For Converging Lens (object beyond F) (p346)

15. Wrap Up Let’s see that again Finding focal point of converging lens (p 346Finding focal point of converging lens (p 346) Ray Diagram Activity 4.21 (p349Ray Diagram Activity 4.21 (p349) WB p140-142

16. 4.6 Lenses - Virtual Images (p350-351)Lenses (p350-351)

17. Warm Up - Recap Activity 4.21 (p349) Using BLM 4-20 complete - “Do” #1-5 - “Find” #1-2

18. Ray Diagrams For Converging Lens (object between F and lens) Let’s Try This: What kind of image?

19. The characteristics of the image of an object placed between F and a converging lens are: (L) the image is farther from the lens than the object (O) the image is upright (S) the image is larger than the object (T) the image is virtual Describe Image if Object is between F and lens (LOST)

20. Converging lenses can produce different types of images The first lens known to be used was a converging lens called a reading stone. Reading stones formed images that were upright and larger than the object. Magnifying glass - Try it yourself !

21. Ray Diagrams For Converging Lens (object between F and lens) (p 351)

23. If the object is between the focal point (F) and the converging lens, a larger (magnified) upright image is formed. Remember that when the object was outside the focal point (F), an inverted image was formed.

24. Wrap Up Converging lens (p351) Text p 350 - LC #1-3 WB p143

25. 4.6 Lenses - Applications (p357)Lenses (p357)

26. Copyright © 2010 McGraw-Hill Ryerson Ltd. Science at Work

27. Applications – Optical Devices a) Eyewear - farsightedness (hyperopia) - use converging lens - nearsightedness (myopia) - use diverging lens

28. Applications – Optical Devices b)Telescope

29. Applications – Optical Devices c) Microscope

30. Wrap Up WB p143 BLM 4-3