1. Reflection of Light
Reflection – the turning back of an electromagnetic wave at the surface of a substance

2. Clear vs. Diffuse Reflection
Specular reflection: light reflected from smooth shiny surfaces
In specular reflection the incoming and reflected angles are equal (=’)
Diffuse reflection: light is reflected from a rough textured surface

3. Part 2 - Reflection Reflection from a mirror: Mirror Normal
Incident ray
Reflected ray
Angle of incidence
Angle of reflection
Mirror

4. Reflection of Light
Angle of incidence – the angle between a ray that strikes a surface and the normal to that surface at the point of contact.
Angle of reflection – the angle formed by the line normal to a surface and the direction in which a reflected ray moves
Normal is a line perpendicular to the reflection surface.

5. Angle of incidence = Angle of reflection
The Law of Reflection
Angle of incidence = Angle of reflection
In other words, light gets reflected from a surface at THE SAME ANGLE it hits it.
The same !!!

6. Drawing a Reflected Image
Use ray diagrams to show image location
We will find the virtual image (the image formed by light rays that only appear to intersect)

8. Drawing a Reflected Image
Draw the object in front of the mirror
Draw a ray perpendicular to the mirror’s surface. Because this is 0 from normal, the angle is the same from the mirror to the virtual object
Draw a second ray that is not perpendicular to the mirror’s surface from the same point to the surface of the mirror.
Next, trace both reflected rays back to the point from which they appear to have originated, that is, behind the mirror. Use dotted lines when drawing lines that that appear to emerge from behind the mirror. The point at which the dotted lines meet is the image point.

9. Flat Mirrors
Image is VIRTUAL, UPRIGHT, UNMAGNIFIED

10. Concave Mirrors

11. Concave Spherical Mirrors
A spherical mirror has the shape of part of a sphere’s surface. The images formed are different than those of flat mirrors.
Concave Spherical Mirror – an inwardly curved, mirrored surface that is a portion of a sphere and that converges incoming light rays.

12. Concave Spherical Mirrors
The light bulb is distance p away from the center of the curvature, C. Light rays leave the light bulb, reflect from the mirror and converge at distance q in front of the mirror. Because the reflected light rays pass through the image point, the image forms in front of the mirror.

13. Concave Spherical Mirror
When an object changes its location in relation to the mirror, its image changes in location, and form.

14. Concave Spherical Mirrors
If you were to place a sheet of paper at the image point, you would see a clear, focused image of the light bulb (a real image). If the paper was placed in front of or behind the image point, the image would be unfocused.

15. Concave Spherical Mirrors
Real image – an image formed when rays of light actually intersect at a single point
Focal length – equal to half the radius of curvature of the mirror.

16. Concave Spherical Mirrors
Mirror equation: 1/p + 1/q = 2/R
= Object distance Image distance radius of curvature
Or: 1/p + 1/q = 1/f =
Object distance Image distance focal length

17. Concave Spherical Mirrors
Object and image distances have a positive sign when measured from the center of the mirror to any point on the mirror’s front side.
Distances for images that form on the backside of the mirror always have a negative sign.

18. Concave Spherical Mirrors
The measure of how large or small the image is with respect to the original object is called the magnification of the image.
M = h’/h = -(q/p)
Magnification = image height = image distance
object height object distance

19. Concave Spherical Mirrors
For spherical mirrors, three reference rays are used to find the image point. The intersection of any two rays locates the image. The third ray should intersect at the same point and can be used to check the diagram.

20. Rules for drawing reference rays
Line drawn from object to mirror
Line draw from mirror to image after reflection 1
Parallel to principal axis
Through focal point F 2 3
Through center of curvature C
Back along itself through C

21. Ray 1

22. Ray 2

23. Ray 3

24. All three rays together

25. Spherical Mirrors - ConcaveF
Image is REAL, INVERTED, and DEMAGNIFIED !!!

26. Concave Spherical Mirror
When an object changes its location in relation to the mirror, its image changes in location, and form.

27. Concave Spherical Mirror
Object’s distance
Type of Image
Location of Image
Greater than focal length
Real and inverted
In front of mirror
At the focal length
Image is infinitely away from mirror and can’t be seen
Between focal point and mirror’s surface
Virtual and upright
Behind mirror

28. Distance greater than focal length

29. Distance = focal length

30. Between focal length and mirror

31. Spherical Mirrors – Concave Object Inside the Focal Point
Image is VIRTUAL, UPRIGHT, and MAGNIFIED

32. Concave Spherical Mirrors

34. M= -(q/p)
We have p, but not q, so we need another equation to find q.
1/p + 1/q = 1/f
We have p and f, so we can solve for q.
1/q = 1/f – 1/p

35. 1/q = 1/f – 1/p
Substitute:
(1/10 cm) – (1/30 cm) = 1/q
Solve:
cm = 1/q
q= 15 cm

36. Now with q we can substitute into the original formula and solve.
M= -(q/p)
M= -(15 cm/30cm)
M= -0.50
This means that the image is smaller than the object and inverted. Therefore it is a real image.

37. Spherical Mirrors - Convex
Convex spherical mirror:
An outwardly curved, mirrored surface that is a portion of a sphere and that diverges incoming light rays
The focal point and center of curvature are situated behind the mirror.

38. Spherical Mirrors - Convex
Convex mirrors take the objects in a large field of view and produce a small image, but give a the observer a complete view of a large area.
Examples:
In stores, the passenger’s side of a car

39. Color
White light is not a single color; it is made up of a mixture of the seven colors of the rainbow.
We can demonstrate this by splitting white light with a prism:
This is how rainbows are formed: sunlight is “split up” by raindrops.

40. Wavelengths of Light Red Light – l = 680 nm Green Light - l = 500 nm
Blue Light - l = 470 nm

41. Adding colours
White light can be split up to make separate colors. These colors can be added together again.
The primary colors of light are red, blue and green:
Adding blue and red makes magenta (purple)
Adding blue and green makes cyan (light blue)
Adding red and green makes yellow
Adding all three makes white again

42. Only red light is reflected
Seeing color
The color an object appears depends on the colors of light it reflects.
For example, a red book only reflects red light:
Homework
White
light
Only red light is reflected

43. (or red and blue, as purple is made up of red and blue):
A pair of purple pants, in addition to being ugly, would reflect purple light
(or red and blue, as purple is made up of red and blue):
Purple light
A white hat would reflect all seven colors:
White
light

44. Using colored light
If we look at a colored object in colored light we see something different. For example, consider the outfit below – I mean, from a physics standpoint, not as a fashion choice:
Shirt looks red
White
light
Shorts look blue

45. In different colours of light this kit would look different:
Red
light
Shirt looks red
Shorts look black
Shirt looks black
Blue
light
Shorts look blue

46. Using filters Red Filter
Filters can be used to “block” out different colours of light:
Red Filter
Magenta Filter