Lenses

Two Types of Lenses:

	Effect on Light	Principal Focus
Converging Lens (Convex)	Causes parallel rays of light to come together (converge) at the principal focus.	The point where rays hitting the lens parallel to the axis all meet.
Diverging Lens (Concave)	Causes parallel rays of light to spread out (diverge) as if they are coming from a focal point behind the lens.	The point where rays hitting the lens parallel to the axis appear to come from (behind the lens).

Types of Images Formed by Lenses

Images are formed at points where light rays from an object appear to come together.

Image Type	Description	Example
Real Image	Formed when light rays actually come together to form an image that can be projected onto a screen.	The image formed on the retina of your eye.
Virtual Image	Formed when light rays appear to come from a location different from where they actually are. The rays do not actually meet, so the image cannot be projected onto a screen.	The image seen through a magnifying glass.

Power of a Lens and Focal Length:

The power of a lens increases with its curvature.

To make a more powerful lens:

• Use a material that focuses light better.
• Increase the curvature of the lens, as a more curved lens will focus light more strongly, resulting in a shorter focal length.