Lab13: Optics-Mirrors and Lenses

Name:

Date:

Objective

-Understand how to use ray diagram and experimental values to find out location and shape of images created by concave mirror and convex lens.

Theory

The image of an object created by mirrors and lenses can be constructed via ray diagram method and using the following equation

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Where is the object distance, is the image distance, and is the focal length.

Procedure for 20 cm focal length Concave mirror

1. Use the above equation to calculate the theoretical image distance by using 20 cm as the focal length for the concave mirror and 55 cm and 65 cm as object distances. Record the values in Table 1.

2. Setup the Optics track with Object (light source) at zero and the concave mirror at 55 cm. Place the half screen in between the object and the mirror. Capture the image on the half screen by adjusting until you find the sharpest image of the object.

3. Record the distance between object and mirror (55 - 0 = 55cm) as object distance. Record the distance between the half screen and mirror as image distance.

4. Repeat the above two steps by placing the mirror at 65 cm and recording the image distance.

5. Calculate the percent error for the above two setups using the following formula.

Percent Error = [(Theoretical value - Experimental value)/Theoretical value] * 100

Table 1: Concave Mirror

Focal length: 20 cm

Object Distance	Describe the Image	Image Distance [Experimental]	Image Distance [Theoretical]	Percent Error
55 cm
65 cm

Draw Ray-Diagram corresponding to data of Table 1:

Procedure for 10 cm focal length double Convex lens

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Where is the object distance, is the image distance, and is the focal length.

1. Use the above equation to calculate the theoretical image distance by using 10 cm as the focal length for the double convex lens and 15 cm and 30 cm as object distances. Record the values in Table 2.

2. Setup the Optics track with Object (light source) at zero and the convex lens at 15 cm. Place the full screen on the other side of the lens compared to the object. Capture the image on the screen by adjusting until you find the sharpest image of the object.

3. Record the distance between object and lens (15 - 0 = 15cm) as object distance. Record the distance between the screen and lens as image distance in Table 2.

4. Repeat the above two steps by placing the lens at 30 cm and recording the image distance.

5. Calculate the percent error for the above two setups using the following formula.

Percent Error = [(Theoretical value - Experimental value)/Theoretical value] * 100

Table 2: Double Convex Lenses

Focallength: 10 cm

Object Distance	Describe the Image	Image Distance [Experimental]	Image Distance [Theoretical]	Percent Error
15 cm
30 cm

Draw Ray-Diagram corresponding to data of Table 2

Questions:

Answer the following post-lab questions.

1. How close is the image distance from theoretical value to experimental value? What can account for the difference?

How can we make the percent error value as minimal as possible?