1. Light and Reflection

2. Characteristics Light is a transverse wave.
Light waves are electromagnetic waves--which means that they do NOT need a medium to travel.
ALL Electromagnetic waves travel with a speed of 3.0 x 108 m/s in a vacuum.
Light waves behave like other waves and have the same characteristics such as amplitude, frequency, and wavelength.
The “brightness” or intensity follows the inverse square relationship.

3. Characteristics of EM Waves continued
Made up of 2 components
electric field & magnetic field
The electric and magnetic fields are perpendicular to each other.
A changing electric field will create a magnetic field and a changing magnetic field will create an electric field; therefore the wave propagates itself through space without need of a medium.

4. Other Electromagnetic Waves
Radio
Microwaves
Infrared
Ultraviolet
X-rays
Gamma Rays
Radar
All of these follow the same rules as Light and travel at the same speed.
Light is simply a way of referring to the visible portion of the electromagnetic spectrum.

5. Reflection & Mirrors

6. Law of Reflection i
incident ray
reflected ray
normal
Mirror surface r
Angles are always measured from the normal, never the surface
Angle of incidence equal angle of reflection
i = r

7. Types of Reflection Specular (regular) Reflection Diffuse Reflection
When parallel rays of light fall on a smooth surface they are reflected parallel from the surface.
Diffuse Reflection
When parallel rays of light fall on a textured surface they are reflected in many different directions. They are diffused.

8. Types of reflection (cont)

9. Plane (flat) mirrors Plane mirrors produce images that are: virtual
same size
(M = 1)
upright
located behind the mirror

10. Spherical (curved) mirrors

11. Concave Mirrors
Reflective surface to the inside of curve, forms a “cave”
Parallel rays of light from a far object will converge at the focal point.
Concave Mirrors also called “converging mirrors”
Focal point is half the distance from the center of curvature (C) to the mirror
The center of curvature is equal to the radius
f = C/2, where C is center of curvature

12. Convex Mirrors
Reflective surface to the outside of curve (back of spoon)
Parallel rays of light from a far object will diverge as if they originated at the focal point.
Convex Mirrors also called “diverging mirrors”
Focal point is half the distance from the center of curvature (C) to the mirror
f = C/2, where C is center of curvature

13. Calculations f = focal length do = object distance di = image distance
hi = image height
ho = object height
M = magnification

14. Using signs correctly Focal length (f)
concave, then f = + convex, then f = -
Image distance (di)
di=+ , then image is real
do= -, then image is virtual
Magnification (M)
M = +, image is erect
M = - , image is inverted

15. Ray Diagram Concave Mirror
Draw 2 rays from tip of object:
1) parallel, then through f
2) through f, then parallel
object
Image is real, inverted, & reduced
image C f

16. Ray Diagram Convex Mirror
Draw 2 rays from tip of object:
1) parallel, then reflect as if ray came from f, ) toward focal point, then parallel, extend reflected ray behind mirror
image
object f C
Image is virtual, erect, & reduced

17. Web-based animation for curved mirrors
Concave mirrors
Convex mirrors