Mirror and Lens Lab
Group members: _________________ ________________ _____________ _______________
Description: The purpose of this experiment is to measure the focal length of two similar lenses.
The magnification and orientation of images produced by each type of lens or mirror will also
observed. The following materials are necessary to perform this lab:
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Small plane mirrors
Concave and convex mirrors
Two different convex lenses (converging lens)
Multiple light sources
White paper
Ruler – metric (cm)
Adjustable optical bench with mounts for the lenses, light source and projection screen
HANDLE LENSES AND MIRRORS WITH CARE. IF DROPPED, THEY WILL BREAK!
Procedure: Follow the directions below and answer all questions. Each group member should
observe the behavior of all mirrors and lenses.
I. Mirrors
a. Plane mirror
1. Take the small plane mirror and measure it’s height in cm.
Mirror height _________cm
2. Hold a ruler beside your face and look at your reflection. How many centimeters do you see?
3. Slowly move the mirror away from your face. Does the number of centimeters you can see
change? Describe what you see.
b. Concave Mirror
1. Hold the concave mirror at arms length away from your face. Describe what you see.
Is the image upright or inverted? Real or virtual? Does the image appear smaller or larger?
2. Slowly move the mirror closer to your face. At what length from your face does the image you
see become completely distorted?
_________cm
3. What happens to the image you see when you move the mirror even closer to your face?
Is the image upright or inverted? Real or virtual? Does the image appear smaller or larger?
c. Convex Mirror
1. Hold the convex mirror at arms length away from your face. Describe what you see.
Is the image upright or inverted? Real or virtual? Does the image appear smaller or larger?
2. Describe what happens to the image as you move the convex mirror closer to your face.
II. Lenses
Formulas: Image height(hi)-
Magnification-
Focal length-
Lens 1- Blue tape
1. Hold the lens above the white piece of paper on your table. Focus the light overhead onto the
page until the image is clear. At what height is the image clear? ________ cm
2. Set up the optical bench as shown in the lab diagram provided on the table. Using the same
lab diagram, measure height of the object, distance to the object, and distance to the image.
Record in table below. Place the lens at 20cm on the optical bench (light base adds 6 cm)
Lens 1 (Blue tape) Keep lens in the same place (only move the index card)
Height of object (ho)
____________ cm
Distance to object (do)
____________ cm
Distance to image (di)
____________ cm
Height of image (hi) *use formula*
____________ cm
3. Show your work for calculating the height of the image:
Image height (hi)- _____cm
4. Calculate the magnification of the lens:
M = _______
5. Describe the image you see: (is it upright or inverted, real or virtual, magnified or reduced)
6. Show work for calculating the focal length of the lens:
Lens 2- Yellow tape
1. Hold the lens above the white piece of paper on your table. Focus the light overhead onto the
page until the image is clear. At what height is the image clear? ________ cm
Place the lens at 30cm on the optical bench for this lens (light base adds 6 cm) Record data below
Lens 2 (Yellow tape)
Height of object (ho)
____________ cm
Distance to object (do)
____________ cm
Distance to image (di)
____________ cm
Height of image (hi) *use formula*
____________ cm
2. Show your work for calculating the height of the image:
Image height (hi)-______cm
3. Calculate the magnification of the lens:
M = _______
4. Describe the image you see: (is it upright or inverted, real or virtual, magnified or reduced)
5. Show work for calculating the focal length of the lens:
Post Lab questions:
1. What happens to the image size if you move the lens closer to the light source?
2. What happens to the image size if you move the lens farther away from the light source?
3. How close are your calculated focal lengths to lengths you measured by holding the lens?