- Review the formation of images by positive lenses - Develop a model to explain the phases of the moon - Work toward completing review problems for light TODAY’S OUTCOMES: BEHAVIOR OF LIGHT

At the movie theatre they use a lens and small pictures in each frame of the film to project really big pictures on the screen. Describe how you could change the system you have been working with to project even larger images that are very big and in focus.

Central to the last activity was the ability to understand image formation every point on the object produces light in all directions - to keep it “simple” we only consider the tip of the object to have a focused image, the light rays from a point on the object must converge at a single point object image

Light rays can be reversed and follow the same path: If you place the object at the image distance, the image will move to the object distance! object image

Light rays can be reversed and follow the same path: If you place the object at the image distance, the image will move to the object distance! object image

In your last lab, you started with a far- away screen (about 1 m) image when lens close to object object image You saw 2 images - the other is just the same situation, reversed image when lens close to screen object image

When the screen moved closer to the object; we needed to move the lens further from the object or screen: image when lens close to object image when lens close to screen These diagrams show what happens when the screen moves closer to the object. object image

If you move the screen closer to the object, you reach a point where the image size equals the object size. Then, the 2 images merge together - you cannot get the screen any closer and stay in focus! lens halfway between object, screen object image

Let’s pull the screen back away from the object... object image

Let’s pull the screen back away from the object... object image object

Let’s pull the screen back away from the object... Back to starting distance again: The distance between the lens and object or screen was close to (but not quite) equal to the focal length focal length The long light beams are close to (but not quite) parallel object image object

If you separated the object and screen by a HUGE distance focal length Beams become (for all practical purposes) parallel. You used this (bottom) method to find the focal length. object object far away image far away image

At the movie theatre they use a lens and small pictures in each frame of the film to project really big pictures on the screen. Describe how you could change the system you have been working with to project even larger images that are very big and in focus. 3) You need an easy way to finely adjust the location of your lens along the projection line, because its distance from the object will control the focus of the image. 4) You will need a brighter light source, because the light will be spread out over a huge screen. 5) You will need as large a lens as possible, to allow more light to be projected on the screen. 2) The lens will need to be close to the source image, but not as close as the focal length. 1) You need much more distance between the source object and the screen.

- How light coming from a point on an object converges to a point on an image - Size of an image and focus is a function of the placement of the lens between the object and image - Where to place a lens to produce larger and smaller images WHAT YOU ARE EXPECTED TO KNOW: