1. Physics
Oct.24, 2014
Open to 5.2
Can you see the buck?
(not the doe)

2. Uses of Mirrors & Lenses
What are some commercial uses of lenses?
Glasses/ Contacts
Projectors
Cameras
Microscopes
Telescopes
Binoculars*

3. Camera

4. Telescope
Clip

5. Binoculars

6. Projector
show HOLT CD animations

7. Microscope
Linked to HOLT CD animations
Clip

8. Mirrors & Lenses
Convex
Concave

9. Mirascope

10. Mirrors & Lenses Converging – light rays come together
Diverging – light rays spread out

11. Types of Images Virtual Image Real Image right-side-up
cannot be projected on a screen
Real Image
upside-down
can be displayed on a screen*

12. Image formation Distance affects the angle of view
Far away- small angle of view allows very little detail to be seen
Closer- larger angle of view creates more details to be seen

13. Ray Diagram Setup
Principal axis- line in a lens that joins the centers of curvature of the lens surface

14. Ray Diagram Setup
Focal point- point at which a beam of parallel light, to the principal axis, converges

15. Ray Diagram Setup
Focal Plane- all possible points on a plane for the location of the focal point

16. Ray Diagram Setup
Focal length- distance between center of lens and its focal point

17. Ray Diagrams:
Copy the instructions on the next few slides and then we will look at the rules in a virtual “draw”.

18. How to draw a mirror ray diagram:
parallel to the axis then go through the focal point.
to the center of the mirror then out at the same angle.*

19. Let’s draw a correct ray diagram
The scope of vision looks like this in yellow.
The first blue ray goes from the top of the object – parallel to the “principal axis” and comes back at the same angle (90) P
Start with a plane mirror. The lines represent the back of the mirror.
We need an object to reflect. Faces are hard to draw. Let’s draw the letter P.
Let’s trace the light rays that will produce an image of the letter P.
When we draw light rays we are creating a ray diagram. In other words a diagram that maps out the rays.
We will pick rays that are helpful in locating specific spots of an object. We’ll draw two rays to help locate the top left corner of the letter P.
There are many more rays we could draw, but two are enough. So we’ll keep it simple.
The first ray we’ll draw (blue) will go straight to the mirror and bounces back at the same angle.
The second ray we’ll draw (red) will go to the mirror at an angle and bounce off at the same angle.
These rays do not intersect so we will need to artificially add some rays that will intersect so we will know where to put the upper left corner of the P’s image.

20. Let’s draw a correct ray diagram
There is no focal point on a flat mirror.
If we are wanting to begin at the top of the ‘P’ - the angle is whatever you choose with the red arrow P
Start with a plane mirror. The lines represent the back of the mirror.
We need an object to reflect. Faces are hard to draw. Let’s draw the letter P.
Let’s trace the light rays that will produce an image of the letter P.
When we draw light rays we are creating a ray diagram. In other words a diagram that maps out the rays.
We will pick rays that are helpful in locating specific spots of an object. We’ll draw two rays to help locate the top left corner of the letter P.
There are many more rays we could draw, but two are enough. So we’ll keep it simple.
The first ray we’ll draw (blue) will go straight to the mirror and bounces back at the same angle.
The second ray we’ll draw (red) will go to the mirror at an angle and bounce off at the same angle.
These rays do not intersect so we will need to artificially add some rays that will intersect so we will know where to put the upper left corner of the P’s image.

21. http://www. regentsprep. org/Regents/physics/phys09/bcraytrace/default

22. How to draw a lens ray diagram:
parallel to the axis then to through the focal point.
straight through the center of lens. *

23. http://www. regentsprep. org/Regents/physics/phys09/bcraytrace/default

24. Let’s draw a correct ray diagramP
Virtual rays are drawn behind the mirror.
Real light rays do not go behind the mirror.
We will draw dotted lines to represent these virtual rays.
Ray 1 (dotted blue): trace the reflected blue ray straight back
Ray 2 (dotted red): trace the reflected red ray straight back
The point of intersection is where the upper left corner of the P will be seen.

25. Let’s draw a correct ray diagramP P
Repeat for the bottom right corner.
Then draw in the image placing the appropriate parts at the intersections.
This image is virtual because we used the “imaginary” lines. We did not use the real rays. This image can NOT be projected on a screen.
The

26. More practice

27. More practice

28. Mirror & Lens Equation distance to image Focal length
distance to object

29. Mirrors and Lenses have many opposite properties.
For a mirror: the positive side is the side the object is on. To remember this, I think "light should reflect off a mirror therefore making that side positive."
For a lens: the object is on the negative side. To remember this, I think, "light should go through a lens therefore making it the positive side." The exception, even though the object is on the negative side, it has a positive distance.

30. Example) Mr. Nelson is showing slides to his physics class, if the slides are positioned 15.5 cm from the projector lens that has a focal length of 15.0 cm, where should the screen be placed to produce the clearest image of the slide?
do = 15.5 cm
f = 15.0 cm
di = ?

31. Power of Eyeglasses Power – measured in diopters (1/meter)
focal length (m)*

32. Example) Beth is farsighted, so she must wear glasses to see objects close by. If her glasses have a focal length of 0.30 m, what is their power in diopters?
P = ?
f = .30 m

33. Image Size
Magnification- image is observed through a wider angle with the use of a lens
image height*
Magnification
object height*

34. Practice Problem
As you look through your binoculars at a deer out in the field, the deer appears to be 3 m tall but the deer in real life is only 1 m tall. How much magnification do your binoculars have?

35. As you look through your binoculars at a deer out in the field, the deer appears to be 3 m tall but the deer in real life is only 1 m tall. How much magnification do your binoculars have?

36. Mirror and Lens Overview

37. Lemony Snickets Clip

38. Talking on a LASER Demo

39.
lab

40. Homework 29s – Review Worksheet Due – Nov. 8th
Worksheets you should have complete:
We will be in the auditorium the next 2 LG’s
Physics Great America – May 19th $50-$55
Start saving now if you plan on going
Need to have a C or better
12s
23s
13s
24s
14s
28s
15s

41. Demonstration on how to print multiple PowerPoint slides on 1 page…