glasses and magnifying glass 1. Find in your house (or among your friends) either a pair of glasses or a magnifying glass. Examine it closely.

a. Draw a sketch of the lens and say if it is a concave lens or a convex lens. How do you know?
2. You will need a magnifying glass for this demonstration. When you are done with the activity, report the focal length of your magnifying glass.

a. Go outside on a sunny day and put the piece of paper on a patch of asphalt, concrete, or a large flat rock. Make sure there is nothing that can catch fire in the area.
b. Hold the magnifying glass so it is close to the rock or concrete, with rays of sunlight shining through it. Move the magnifying glass side to side and close or away from the ground until the most concentrated ray of light is shining on the ground. This is the focal point for that magnifying glass.
c. Measure the distance between the ground and the magnifying glass after you have found the focal point. This is the focal length for that magnifying glass. (Be careful; if you hold the magnifying glass in that place for long enough, the ground could catch fire. Do not ever do this on your skin or clothing, as it can cause serious burns).