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The video below shows a typical lens experiment. (reference to O-Level SciPhy 2015). I will briefly go through the set-up, main steps and how to get the 1st set of readings.
In the next video, it highlights the various types of lens practical which you might have in the school lab. e.g. different kind of crossed-wire, a beaker of water as a converging lens and different kind of images formed.
Key points:
1) Make sure the object (illuminated crossed-wire), lens and screen are aligned properly.
2) Source of Error: identifying the sharpest image
Improvement:
(i) Repeat the experiment a few times for the same independent variable to identify the sharpest image.
(ii) Move the lens (or screen) forward and backward about the sharp image, until the sharpest image is determined.
3) In general, the focal lens of the lens used in the lab is usually 10 cm or 15 cm. Most lens experiment requires you to find the focal length. There is also a easy way to quickly determine the focal length before starting the experiment.
