images and ray diagrams

• a real image is where the light from an object comes together to form an image on a screen
• a virtual image is when the rays are diverging, so the light from the object appears to be coming from a completely different place
• need to be able to draw, read.

  
• read and practice

  
• concave lenses always produce a virtual image, and convex a real image
• a concave image is the right way up, smaller (diminished) than the object and on the same side of the lens as the object
• magnifying glasses uses convex lenses. the object must be closer to the lens than the focus length. the light rays don't actually come from the place where the image appears to be. you can't project a virtual image onto a screen.
• magnification = image height / object height
• look at free science lessons video