Purpose:
If you light a candle in a darkened room and place a convex lens between the candle and a paper screen, an upside down image of the candle will appear on the screen! You may have to adjust the spacing of the candle object, lens and screen to get a crystal clear image. Carefully measuring the distance from the candle to the lens (do) and from the lens to the screen (di) will reveal that this arrangement follows the lens equation: f = 1/(1/di + 1/do)

Setup:

• The optics bench Java applet should be presently running under Procedure:
• Click the Lens button and place the lens in the middle of the 5 unit x-axis at 2.5. The lens should automatically start with a focal length of .5 (If not, just grab the focal point handles and drag until it is adjusted to the correct length)
• Click the Object button and place the the arrow-like object at 1.5 (do=1)
• Understand that the far left of the x-axis is 0 and the far right is 5
• Understand that the object distance (do) and the image distance (di) is measured from the lens, so do is actually 2.5 - 1.5 or 1 and di is actually 3.5 - 2.5 or 1

Procedure:

1. Use the Data: table below and the equation f = 1/((1/di)+(1/do)) to solve for the missing variable
2. Check your answer with the applet by setting up your lens and object for each of the 9 problems
3. To properly place the object and interpret the image distance may be confusing for some since do and di are measured from the lens so x = (2.5 - do) for the arrow-object and x = (di + 2.5) for the arrow image
4. To adjust the lens just click on the lens and grab/drag the focal points