29 May 2015
Objective: Calculate the focal length of a converging lens and understand its image-forming characteristics.
Hypothesis: Will putting the lens closer to the focal length on the meter stick make the image clear?
Object screen Cobalt-glass filter
Meter stick with supports Candle
Cardboard screen with metric scale
Double convex lens
1. Focal Length
A. The experimenter should put a cardboard screen and a converging lens on a meter stick. The experimenter should place the lens at the 50cm mark and the screen near the 70cm mark. He/she should adjust the meter stick until the image appears on the screen. The distance from the lens to the screen may be taken as the focal length of the lens. He/she should record the focal length. Then, he/she should move the lens to the 60cm position and repeat the procedure using a different distant object.
2. Formation of images B. The experimenter should place a lighted candle at one end of the meter stick. Next, he/she should make adjustments to the object screen coincides with the principal axis of the lens. Then, he/she should move the image screen along the meter stick until the image screen is as well defined as possible. Finally, he/she should record the positions of the object, lens, and image. C. For a second trail, the experimenter should place the lens at a position for an object distance just twice the focal length of the lens. Then, he/she should adjust the meter stick until the image appears on the screen. Record all the positions. D. For the third trail, he/she should locate the lens between one and two focal lengths from the object screen. Then, find the image and record all the positions. E. The experimenter should place the lens so that it is exactly one focal length away from the object. Try to form an image. F. Then he/she should put the lens so that it is less