1. Wave Motion Common Mistakes (with Quick Quiz) 1 Ch. 19 Lenses (Sample)

2. Wave Motion Common Mistakes 2

3. Wave Motion 1.Focal plane and principal focus 3 Light rays from different points at infinity should focus on different points on the focal plane. HKCEE 2010 Paper 2 Q14 HKDSE 2014 Paper 1B Q6

4. Wave Motion 2.Position of image 4 Light rays from the head (tail) of the object focus on (or appear to diverge from) the head (tail) of the image. HKCEE 2010 Paper 2 Q14 HKDSE 2012 Paper 1B Q7

5. Wave Motion 3.Paths of light rays 5 The light rays should pass through the image (not stop at it).

6. Wave Motion 4.Object and image positions Mind the positions of the object and the image. They may not lie on the principal axis. 6

7. Wave Motion 5.Position of the lens For a fixed object–image separation, there are two positions for the lens to form a sharp image. One gives a magnified image and the other one gives a diminished image. 7

8. Wave Motion A convex lens can produce a magnified real image or a magnified virtual image. Pay attention to the nature of the image produced when answering related problems. 6.Magnified images 8

9. Wave Motion Quick Quiz 9

10. Wave Motion Which diagram is correct? A.B. Question 1 10

11. Wave Motion Question 2 11 An illuminated object O is placed in front of a convex lens and forms a diminished image on a screen on the other side. When the object and the screen exchange their positions, …

12. Wave Motion Question 2 (cont’d) 12 When the object and the screen exchange their positions, A.a sharp image will still be formed on the screen. B.an image will still appear on the screen, but it is blurred. C.no image will be formed on the screen at all.

13. Wave Motion Question 3 13 In question 2, when the object and the screen exchange their positions, A.the image formed becomes even smaller. B.the image formed becomes bigger.

14. Wave Motion Question 4 14 In question 2, if the upper half of the lens is covered, A.no image will be formed on the screen. B.the image formed becomes dimmer.