1. Unit 8, Lesson 7
Convex Lenses

2. concave
convex
(Diverging) lens
(Converging) lens

3. Convex (converging) lensf f
Principle axis

4. Image through a convex lens
Try This: Describe the image if do = 1.5f and f = 20 cm.
Image Characteristics:
do = 30 cm
size –
location –
type –
attitude –
larger
further
real
inverted f f
10 min

5. Image through a convex lens
Try This: Describe the image if do = 0.5f and f = 20 cm.
Image Characteristics:
do = 10
size –
location –
type –
attitude –
larger
further
virtual
upright
10 min f f

6. Brain Break!

7. convex lens calculations
Example: Describe the image if do = 1.5f and f = 20 cm.
do = 30cm 1 f 1 do 1 di = + 1 f 1 do 1 di = + hi ho
-di do
M = = 1 20 1 30 1 di = + 1 1 20 1 30 1 60 = - = di
Image Characteristics:
5 min
di = 60 cm
size –
location –
type –
attitude –
bigger
60 cm opposite
-di do
-60 30 M = =
= - 2X
real
inverted

8. convex lens calculations
Try This: Describe the image if do = 0.5f and f = 20 cm.
do = 10cm 1 f 1 do 1 di = + 1 f 1 do 1 di = + hi ho
-di do
M = 1 20 1 10 1 di = = + 1 1 20 1 10 1
-20 = - = di
10 min
Image Characteristics:
di = -20 cm
size –
location –
type –
attitude –
bigger
20 cm on same side
-di do
-(-20) 10 M = =
= 2X
virtual
upright

9. Homework:
Pg. 252 #5 and 6
10 min

10. Unit 8, Lesson 8
Concave Lenses

11. Concave (Diverging) lensesf

12. Ray Rules for concave lenses
Principle axis

13. Try This: Locate and characterize an image formed in a diverging lens of focal length 10 cm if do = 15 cm. (Show using a ray diagram + equations.) f f 1 f 1 do 1 di = +
20 min 1
-10 1 15 1 di = +
Image Characteristics: 1 1
-10 1 15 1 -6 = - =
size –
location –
type –
attitude –
smaller
di = -6 cm di
6 cm on same side
virtual
-di do
-(-6) 15 M = =
= +0.4X
upright

14. Brain Break!

15. Example: Where should an object be placed if an upright virtual image half its size is to be formed by a concave lens of focal length 10 cm? 1
-10 1 do 1 di 1
-10 1 do 1
-0.5do = + = +
-di do 1 2 M = = 1 1 do 2 do -1 do = - =
-10
di = -0.5do
do = 10 cm
15 min f

16. Homework:
Optics Review sheet!
10 min