Optics: Mirrors and Lenses
For this lab you will be verifying the focal lengths of concave mirrors and lenses as provided by the
manufacturer.
For this lab you first must design a procedure for determining the focal length of a concave mirror or lens using
only a candle, holder, meter stick and screen. Consider the following questions while designing your
experiment:
1. What equation can be used to determine focal length?
2. What variables can you control in that equation? (Hint: This should be your independent variable)
3. What variables can you measure in that equation? (Hint: This should be your dependent variable)
Once you have designed your procedure you must collect a sufficient amount of data for the mirror and lens.
For the data analysis section, you will linearize the equation you used in developing the procedure to obtain a
graph that can be used to determine the focal length. Include a description of what should be graphed in order
to obtain a line that can be used to determine f. DO NOT plug the numbers into the formula, you must use
linearization and the graph (along with linear regression) to determine the experimental value of f. For your
conclusion, discuss how close your values are to the published values given by the manufacturer and whether
the mirror or lens were closest from the accepted value and why you think this is. Be sure to include a
discussion of improvements and sources of error (DO NOT say human error or incorrect use of a meter stick)
for the lab.
PROCEDURE FOR FINDING FOCAL LENGTH OF A DIVERGING LENS: