Return to Honors Physics Home Page (Revised 4-12-06)
Reflection of Light – Spherical Mirrors Lab
Purpose:
Materials:
Data Table: Construct your own Microsoft Word data table having the following variables:
|
Case # |
FEXP |
PEXP |
QEXP |
QMATH |
SO |
Si EXP |
Si MATH |
MQ/P |
MSi/So |
%ERROR |
|
(cm) |
(cm) |
(cm) |
(cm) |
(cm) |
(cm) |
(cm) |
|
|
|
Procedure: (A written procedure is not required. Simply follow the procedure written below)
Each case requires a completely labeled two-ray diagram.
The “object” in each case is the illuminated arrow located in the window of the projector (Photo # )
Case #1: Establish fEXP by aligning the mirror/projector in such a way that the image produced projects
onto the index card held to one side of the projector (Photo # ). C = 2fEXP, so fEXP = C/2.
FMATH is found by employing the mirror equation, where:
P = Q at C. Measure the distance from object and image to mirror, then place this common value into the equation for P and Q.
NOTE: For each of the following cases, you must have a visual memory of your mirror’s focal length, from which to estimate your mirror/index card placements.
Case #2: Once fEXP has been established in Case #1, Use this value for Case #2 and all subsequent cases. Move the mirror away from the projector to a distance, P = (4)f [P = (5)f for 2003 lab]. The resulting real image should be located between f cm and 2f cm from the mirror, and can be focused onto an index card. QEXP can be measured by using a metric stick. SiEXP can be measured by placing a metric ruler vertically to the side of the focused image. SoEXP is the length of the arrow on the projector, and remains constant throughout the lab.
Case #3: Adjust the distance between the projector and mirror so P = (3)f. [P = (3.5)f, 2003 lab]
Case #4: The mirror is moved closer to the projector to a distance P = (1.75)f. [P = (2.0)f, 2003 lab]
Case #5: The mirror is moved closer to the projector to a distance P = (1.25)f. [P = (1.5)f, 2003 lab]
Case #6: The mirror is moved closer to the projector to a distance P = (0.5)f. [P = (0.5)f, 2003 lab]
Sample Calculations:
The solution for QMATH, SiMATH, MQ/P, MSi/So, %E must be shown for each case. "f" used in each solution (Case #2 through Case #6) is the focal length determined during Case #1. QMATH is found using the mirror equation, 1/P + 1/Q = 1/f. When solving for SiMATH, use QMATH / PEXP = SiMATH / SoEXP. When solving for MQ/P, use QMATH / PEXP. When solving for MSi/So, use SiEXP / So. Use the formula %E = [(MQ/P - MSi/So) / MQ/P] x 100
Conclusion:
(1) By what two methods could the focal length of your mirror have been determined? Diagram each. Which method would seem to be more reliable? Why?
(2) For case #4 compare /contrast QEXP and QMATH (state one similarity, one difference) . Compare/contrast QEXP and QMATH for case #6 as well. Explain, using specific data values. When contrasting the two image values, state two specific potential errors in lab technique to account for recorded differences. Don't compare values between cases.
(3) For each case given above, explain WHY the magnification calculated has the value it has. Substantiate using specific data values.
(4) State the case (other than case #1 or #4) having the LEAST percentage error in your lab results. Explain how the mechanics of the case permit this value. Substantiate using specific data values.
(5) Repeat problem #4, discussing the case having the GREATEST percentage error. Substantiate using specific data values.
Sources of Potential Lab Error: (Not necessary to list sources of error. Include these in your discussion of conclusion problems above)
Practice Problems: Refer to Reflection Short Answer problems. Answer any three (3) from the following: #2, 3, 4, 5, 9, 12.