Ray Diagrams

Here is a ray diagram showing how a convex lens produces an INVERTED IMAGE. The lens and cornea of your eye works in just the same way. The image on your retina (the back of the eye) is upside down, but your brain sorts this out. In this diagram the magnification is times 2. The image is twice as large
as the object.

Follow the 14 diagrams below to draw your own ray diagram for a convex lens. Make sure that you use a sharp HB pencil and a 30cms ruler. It is best to do the drawing on squared paper so that you get the optic axis at right angles to the lens and the parallel rays of light parallel.

You can change the values for the image height and distance and for the focal length, but some values will give you a smaller image than the object and some values will not give an image at all. I hope that you can read my handwriting. 1. Here I have drawn the optical axis (a horizontal line). 2. Now I have added the position of the lens (a vertical line). 3. This shows that it is a convex lens. 4. Now I have drawn a vertical line to show the object position. 5. I have drawn a burning candle (this is the object). 6. I have added a ray of light (a straight line through the centre of the lens). 7. Now another ray of light parallel to the optical axis. 8. This ray of light is “refracted” through the centre of the lens. 9. A ray of light through the focal point will be refracted by the lens. 10. That ray is refracted by the lens parallel to the optical axis. 11. Arrows have been added to show which way the light rays travel. 12. I have now drawn a dotted line to show where the image is formed. 13. Here I have drawn the image of the candle over the dotted line. 14. Finally I have divided the image size by the obect size to find the magnification.
When you look at something like another person, the image on your retina
is smaller than the object, so the magnification is LESS than one.

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