1. Light Bouncing Off an Object
Reflection
Light Bouncing Off an Object

2. Reflection and optics- mirrors
When light strikes the surface of an object, some of the light is reflected while the remaining light is either absorbed as thermal energy or transmitted through the object.
Two types of reflection:
Diffuse – from rough surfaces of object results in you being able to see object (like a car)
Specular- from very shiny objects like seeing you reflection in a car hood.

3. Diffuse Specular

4. Diffuse Vs. Specular

5. Both types of reflection can occur from the same surface at the same time. You can see the color of a car while you can see your reflection in the hood.

6. Plane mirrors
When you look at yourself in a plane (flat) mirror, you see what appears to be yourself and the objects around you as if they exist behind the mirror. What you actually see is and image of yourself and the objects around you and the image is reversed. Move your right hand and the image moves its left.

7. Types of images
Optical devices, mirrors, or later lenses, can produce one of two types of image.
A real image- one produced by the convergence of light at the image point. Can actually be projected onto a screen.
Virtual image- light appears to have diverged from the image point without actually passing through that point.

8. We represent light as rays emanating from an object

9. The rays scatter from the bottle in all directions, but the only ones detected by the eye are those that travel from the bottle to the mirror, reflect and hit the eye. How far behind the mirror does the image appear to be? By using geometry, it is found that with plane mirrors, di = do. The image appears to be the same distance behind the mirror as the object is in front of the mirror.

10. Do the rays of light entering the eye actually pass through the image of the bottle? No, they are only reflected off the mirror and interpreted by our eye to come from behind the mirror. The dashed lines are the apparent rays emanating from the image behind the bottle. This is a virtual image.

12. When mirrors are flat they always produce an image that is impossible to touch. It is a virtual image.
Other types of mirrors can be used as optical devices to produce images that can be projected onto a screen in the real world. . They are curved rather than planar. These curved mirrors are a small part of a sphere and can be reflective on either the inside of the sphere, concave, or the outside of the sphere, convex.

13. Concave mirrors
If do is very large compared to the size of the mirror, the rays which strike the mirror are assumed to be parallel.
These parallel rays will not converge at a single focus unless the mirror is small compared to the radius of curvature of the mirror.

15. The focal point is the point at which reflected rays cross the principle axis. It is also the image point for an object infinitely far away. Focal length = r/2.
For images that are not infinitely far away we must use ray diagrams to determine the position of the image.

17. Ray diagrams can be hard to draw accurately, but we can use equations to calculate image specifics.
ho/hi = do/di from this we can derive
= 1
do di f
the mirror equation. The images produced by curved mirrors will be different in size from the object.

18. The magnification is:
m = hi/ho = - di/do
The negative sign is by convention, when ho or hi is positive, the image and object are on top of the principle axis. If negative they will be below the axis.
di and do are positive when they are both on the same side of the mirror. di will be negative when the image is behind the mirror.
These equations will be good for both types of mirror. The ray diagram produce a different image when the object is placed between the focus and the mirror.

19. A 1. 50 cm high object is placed 5
A 1.50 cm high object is placed 5.0 cm form a concave mirror whose radius of curvature is 6.0 cm. Determine:
The position of the image and the size of the image.
1/5 + 1/di = 1/3 di = 7.3
m = -7.3/5.0 = -1.46
m(h0) = hi = cm
Image is 1.5 times larger than the object and appears below the p axis.

21. Convex mirrors
When the reflective surface is on the outside of the sphere, the mirror is convex.
The images produced by convex mirrors will be virtual.
The mirror equations will be the same for either concave or convex mirrors.

23. The mirror equations will be the same for either concave or convex mirrors.