1. Thin Lenses-Intro Notes
A lens forms images by refracting (bending) light while a mirror reflects light

2. The Focal Point
Light rays from an object that is very far away are nearly parallel
The focal point of a lens is the place where the refracted light waves from a distant object converge (or appear to converge)

3. The focal length
The focal length is the distance from the focal point to the center of the lens

4. Converging Lens
A converging Lens is thicker in the middle. A converging lens will refract light waves so that they will “converge” to form an image.
Also called a convex lens

5. Converging Lens A converging lens can produce a real or virtual image
When an object is located at a distance that is greater then the focal length, the image produced is real.

6. Converging Lens
When the object is located at a distance that is between the lens and the focal point, the image is virtual

7. Diverging Lens
A diverging lens is thinner in the middle. Rays of light that pass through a diverging lens will refract outward
Also called a concave lens

8. Diverging Lens A diverging lens will produce only virtual images
The image produced will be smaller than the object
The image will be inside of the focal point

9. Examples of Converging and Diverging Lenses

10. Thin-Lens Equation 1/p + 1/q = 1/f Where:
p = distance from object to lens
q = distance from image to lens
f = focal length

11. Signs For Lenses
p is positive when the object is in front of the lens p is negative when the object is in back of the lens

12. Signs for lenses q is positive when the image is in back of the lens
q is negative when the image is in front of the lens

13. Signs for lenses f is positive for a converging lens
f is negative for a diverging lens

14. Example Problem
An ant is placed 2 cm in front of a converging lens that has a focal length of 1 cm. What is another name for this lens? Where is the image located?