1. From last week- Light

2. Last time
Light is ?
Particle
Wave
Both
Neither

3. Last time Which color has the largest wave length? Red
Which color has the shortest frequency?
Which wave has the longest wavelength?
Radio waves

4. Last time What is dispersion?
Separation of visible light into different colors.
Name the 3 properties of light?
Light travels in straight lines
Reflection- light reflects
Refraction- light bends with a transparent medium.

5. Reflection and mirrors

6. Geometrical Optics
In the study of how light behaves, it is useful to use “light rays” and the fact that light travels in straight lines.
When light strikes the boundary between two media, three things may happen: reflection, refraction, or absorption.
reflection
refraction
absorption
Water
Air

7. Reflection, Refraction, & Absorption
Water
Air
reflection
Reflection: A ray from air strikes the water and returns to the air.
refraction
absorption
Refraction: A ray bends into the water toward the normal line.
Absorption: A ray is absorbed atomically by the water and does not reappear.

8. The Laws of Reflection
1. The angle of inci- dence qi is equal to the angle of reflection qr :
Water
Air N
reflection qr qi
qi = qr
All ray angles are measured with respect to normal N.
3. The rays are completely reversible.
2. The incident ray, the reflected ray, and the normal N all lie in the same plane.

9. reflection

10. The Plane Mirror
A mirror is a highly polished surface that forms images by uniformly reflected light.
Note: images appear to be equidistant behind mirror and are right-left reversed.

11. Definitions
Object distance: The straight-line distance p from the surface of a mirror to the object.
Image distance: The straight-line distance q from the surface of a mirror to the image.
Object
Image
Object distance
Image distance =
p = q p q
qi = qr

12. Real and Virtual
Real images and objects are formed by actual rays of light. (Real images can be projected on a screen.)
Real object
Virtual image
Light rays
No light
Virtual images and objects do not really exist, but only seem to be at a location.
Virtual images are on the opposite side of the mirror from the incoming rays.

13. Image of a Point Object
Plane mirror
Real object p
q = p q
Virtual image
Image appears to be at same distance behind mirror regardless of viewing angle.

14. Image of an Extended Object
Plane mirror p q
q = p
Virtual image
Image of bottom and top of guitar shows forward-back, right-left reversals.