1. Describe what a lens and a mirror do to light rays.

2. Draw a diagram that shows how light travels from an object to a mirror, then to your eyes.

3. Light and Optics

4. 8.1 Maxwell’s Equation

5. After the work of Oerseted, Ampere and Faraday
James Clark Maxwell – all
electric and magnetic
phenomena can be
described by four equations
Fundamental – even taking into account relativity
Require Calculus
8.1 Maxwell’s Equation

6. Gauss’s Law – relates electric field to electric charge
Magnetic field Law –
Faraday’s Law – electric field is produced by magnetic field
Ampere’s Law – magnetic field produced by an electric current, or changing electric field
8.1 Maxwell’s Equation

7. 8.2 Production of Electromagnetic Waves

8. 8.2 Production of Electromagnetic Waves
How Electromagnetic Waves are Produced
The charged particle oscillate
As it travels one direction a current is produced
This generates a magnetic field
When the direction changes, so does the current and the magnetic field
EMR Production
8.2 Production of Electromagnetic Waves

9. 8.2 Production of Electromagnetic Waves
Electric and magnetic fields are perpendicular to each other
The fields alternate in
direction
These are
electromagnetic waves
Transverse
In general – accelerating electric charges give rise to electromagnetic waves
8.2 Production of Electromagnetic Waves

10. 8.3 Electromagnetic Spectrum

11. 8.3 Electromagnetic Spectrum

12. 8.3 Electromagnetic Spectrum
All EMR has a velocity of
in a Vacuum
Velocity decreases with increase in
optical density
The wave equation becomes
Unlike Sound – energy depends on frequency
8.3 Electromagnetic Spectrum

13. 8.4 The Ray Model of Light

14. Light travels in a straight line in most cases (away from very large gravitational fields)
Ray Model – Light
travels in
straight line
pathways called
rays
represents a narrow beam
of light
8.4 The Ray Model of Light

15. We see an object when rays of light come from the object to our eyes
8.4 The Ray Model of Light

16. 8.5 Reflection

17. When light strikes an object it is
Reflected – bounces off
Refracted – transmitted through
Absorbed – converted to a different form of
energy
Law of Reflection
8.5 Reflection

18. Diffuse Reflection – on a rough surface
Rays don’t form an pattern
We see color
Specular Reflection –
smooth surface
Patterns form images
8.5 Reflection

19. What is the speed of light in a vacuum?
If the wavelength of light is 512 nm, what is the frequency?
What would be the energy in a photon of that frequency?
S-100

20. How are images formed Your eye sees the intersection of rays
from an object
Applet
8.5 Reflection

21. Object Distance – from mirror to the object
Image Distance – from mirror to the image
Virtual Image – imaginary intersection of light rays
Real Image – actual intersection of light
8.5 Reflection

22. A man stands in front of a mirror. He is 1. 8 m tall
A man stands in front of a mirror. He is 1.8 m tall. What is the minimum height the mirror must be for him to see his entire image?
S-101

23. 8.6 Formation of Images by Spherical Mirrors

24. 8.6 Formation of Images by Spherical Mirrors
Spherical Mirrors – form a section of a sphere
Convex – reflection on outer
surface of sphere
Concave –
reflection on
inner surface
of sphere
23.3
8.6 Formation of Images by Spherical Mirrors

25. 8.6 Formation of Images by Spherical Mirrors
Terms
Principal Axis – straight line normal to the center of the curve
Focus – point where parallel rays intersect
Vertex – center of the mirror
Focal Length – distance from vertex to focus
Images from distant objects are produced at the focal point
8.6 Formation of Images by Spherical Mirrors

26. 8.6 Formation of Images by Spherical Mirrors
The focal point is actually an approximation
The greater the curve of a mirror, the worse is the approximation
Called
Spherical
Aberration
Examples of Visual
Aberrations
8.6 Formation of Images by Spherical Mirrors

27. 8.6 Formation of Images by Spherical Mirrors
All rays follow the law of
reflection
Two Rules
A ray parallel to the principle axis reflects through the focal point
A ray through the focal point reflects parallel
Examples of Diagrams – Concave Mirrors
Real Images
Virtual Image
8.6 Formation of Images by Spherical Mirrors

28. 8.6 Formation of Images by Spherical Mirrors
Convex Mirrors only form virtual images
Rules
Rays parallel to the principle axis reflect away from the focal point
Rays headed for the focal point reflect parallel
8.6 Formation of Images by Spherical Mirrors

29. Sketch the image formed by. a 2. 00 m tall dog standing. 4
Sketch the image formed by a 2.00 m tall dog standing m from a convex mirror with a focal length of 1.50 m.
S-102

30. 8.6 Formation of Images by Spherical Mirrors
Curved Mirror Equations
ho-object height
hi-image height
do-object distance
di-image distance
The Mirror Equation
Magnification
8.6 Formation of Images by Spherical Mirrors

31. 8.6 Formation of Images by Spherical Mirrors
Sign Conventions
Image Height
+ upright (virtual)
- inverted (real)
Image and Object Distance
+ front of mirror
- behind mirror
Magnification
+ upright image
- inverted image
8.6 Formation of Images by Spherical Mirrors

32. 8.6 Formation of Images by Spherical Mirrors
Sign Conventions
Focal Length
+ concave mirror
- convex mirror
8.6 Formation of Images by Spherical Mirrors

33. 8.7 Index of Refraction

34. Index of Refraction – the ratio of the speed of light in a vacuum to the speed in a given material
NaCl
1.54
Air at STP
Polystyrene
1.57
Water
1.33
Flint Glass
1.65
Quartz
1.46
Sapphire
1.77
Crown Glass
1.53
Diamond
2.417
8.7 Index of Refraction

35. Value can never be less than 1
Material
Index
Vacuum
NaCl
1.54
Air at STP
Polystyrene
1.57
Water
1.33
Flint Glass
1.65
Quartz
1.46
Sapphire
1.77
Crown Glass
1.53
Diamond
2.417
8.7 Index of Refraction

36. 8.8 Refraction: Snell’s Law

37. 8.8 Refraction: Snell’s Law
Refraction – when a ray of light changes direction as it changes media
The change in angle depends on the change in velocity of light (or the index of refraction of the two media)
8.8 Refraction: Snell’s Law

38. 8.8 Refraction: Snell’s Law
Snell’s Law – relates the index of refractions and the angles
Also called the Law of Refraction
If light speeds up, rays bend away
from the normal
If light slows down, rays bend
toward the normal
8.8 Refraction: Snell’s Law

39. 8.8 Refraction: Snell’s Law
Refraction occurs when one side of the wave slows down before the other
8.8 Refraction: Snell’s Law

40. 8.9 Total Internal Reflection; Fiber Optics

41. 8.9 Total Internal Reflection; Fiber Optics
When light travels into a more optically dense medium, the ray bends away from the normal
As the angle increases, the angle of refraction eventually reaches 90o.
This is called the critical
angle
8.9 Total Internal Reflection; Fiber Optics

42. 8.9 Total Internal Reflection; Fiber Optics
Above the critical angle, light reflects following the law of reflection
Used in fiber optics
8.9 Total Internal Reflection; Fiber Optics

43. A frog stands 12 cm in front of a concave mirror with a focal length of 15 cm. The frog is 9 cm tall.
What is the distance and height of the image?
What would be the distance and height of the image if the mirror was convex?
S-103

44. 8.10 Thin Lenses; Ray Tracing

45. 8.10 Thin Lenses; Ray Tracing
Thin lens – very thin compared to its diameter
Diagrams are similar to mirrors
Converging – rays converge
8.10 Thin Lenses; Ray Tracing

46. 8.10 Thin Lenses; Ray Tracing
Converging Lenses
A ray parallel to the Principle Axis refracts through F
A ray through F’ refracts parallel.
A ray through the optical center, O, does not refract
Converging Lens
8.10 Thin Lenses; Ray Tracing

47. SOLAR COOKING
On a Balmy Winters Day!
S-104

48. A diverging lens with a focal length of 18 cm is used to produce the image of a rather cute rodent that is 1.3 cm tall. The rodant stands 22 cm from the lens.
What is the distance, height, and magnification of the image?
What would it be if the lens was converging.
S-105

49. A converging lens produces an image of an stinky fruit 17 cm from the lens. The object was originally placed 12 cm from the lens, and the image is projectable.
A. What is the focal length of the lens?
B. What is the magnification of the image?
S-106

50. A diverging lens produces an image of an cat with a bad haircut 17 cm from the lens. The object was originally placed cm from the lens.
A. What is the focal length of the lens?
B. What is the magnification of the image?
S-107

51. 8.10 Thin Lenses; Ray Tracing
Diverging Lens – spreads apart rays of light
Only produces virtual images
Rules
Parallel rays refract
away from F’
Rays headed toward
F refract parallel
Rays through O do not
refract
8.10 Thin Lenses; Ray Tracing

52. 8.11 The Thin Lens Equation: Magnification

53. 8.11 The Thin Lens Equation: Magnification
Equations are similar to Mirrors, conventions are different
The Thin Lens Equation is
To Calculate Magnification
8.11 The Thin Lens Equation: Magnification

54. 8.11 The Thin Lens Equation: Magnification
Conventions
Focal Length
+ converging lens
- diverging lens
Object Distance
+ same side as original light
- different side (only when more than 1 lens)
8.11 The Thin Lens Equation: Magnification

55. 8.11 The Thin Lens Equation: Magnification
Conventions
Image Distance
+ opposite side from light
- same side as light
Height
+ upright
- upside down
8.11 The Thin Lens Equation: Magnification

56. 8.12 Combinations of Lenses

57. 8.12 Combinations of Lenses
Many devices used combinations of lenses
Combination problems are treated
as separate lenses
Calculate or draw the image from the first lens
Applet
8.12 Combinations of Lenses

58. A hamster shoots a laser
A hamster shoots a laser. It hits a side of a block at an angle of 15o to the normal. At what angle will the ray exit the block. (n=1.51)
q=42o
S-108

59. Test Test Test Test
q=42o
S-109