Reflection of Light in Plane Mirrors
Purpose of Experiment
To compare the angle of incidence with the angle of reflection in a plane mirror.
Equipment and Materials
Ray Box: For emitting light rays.
Plane Mirror: The reflective surface for the experiment.
Mirror Supports: To hold the mirror in place during the experiment.
Pencil and Ruler: For drawing lines and making measurements.
Protractor: To measure angles accurately.
Sheet of Paper: The base for conducting the experiment.
Safety Note
When unplugging the ray box, it is essential not to pull the electric cord. Always pull the plug itself to ensure safety.
Procedure
Setup:
Draw a dashed line across the center of a sheet of paper.
Place the plane mirror along this line. Note that the back of the mirror (the silvered part) should be on the line, as it is the part that reflects light, not the glass part.
Prepare Incident Ray:
Using the ray box, place a slit mask to ensure only one ray of light is emitted.
Aim the emitted incident ray towards the mirror.
Draw Normal Line:
At the point where the incident ray strikes the mirror, draw a normal line which is perpendicular to the mirror's surface. Label this line as "normal" (Refer to Figure 1).
Indicate Ray Paths:
Use a pencil to place several dots illustrating the path of the incident ray.
After, mark several dots along the path of the reflected ray.
Draw Incident and Reflected Rays:
Remove the ray box and the mirror.
With a ruler, draw a straight line through the incident ray dots until reaching the top of the intersection of the normal and mirror, labeling this line as "I1" (incident ray).
Repeat for the reflected ray, labeling it as "R1".
Measure Angles:
Utilize a protractor to measure both the angle of incidence and the angle of reflection from the normal for the first trial.
Record both angles of measurement in the designated table under "Trial 1" (refer to Table 1).
Observational Details
Plane Mirrors in Everyday Life:
Common examples include:
Bathroom mirrors when brushing teeth.
Rear-view mirrors in vehicles.
Dental mirrors used for examinations of the mouth.
Skills Developed
Questioning, Hypothesizing, Predicting, Planning, Controlling Variables, Performing, Observing, Analyzing, Evaluating, Communicating
Skills Menu indicates various skills engaged throughout the experiment.
Data Collection Table Template
Trial Number | Angle of Incidence | Angle of Reflection |
|---|---|---|
1 | ||
2 | ||
3 | ||
4 | ||
5 |
Additional Trials
Repeat Trials:
Conduct steps 1 to 6 three additional times, labeling new incident rays as "I2," "I3," and "I4" and the corresponding reflected rays as "R2," "R3," and "R4."
Ensure the ray box is at a different angle for each trial, but always pointed at the same intersection of the mirror and the normal.
Complete the data table for trials 2 to 4.
**Fifth Trial:
For this trial, align the incident ray directly along the normal line.
Complete the data table for trial 5.
Analysis and Evaluation Questions
(a) Comparison of Angles: How did the angle of incidence compare with the angle of reflection?
(b) Special Case Evaluation: In trial 5, when the incident ray was directed along the normal, describe the behavior of the incident and reflected rays.
(c) Error Investigation: Identify potential sources of error during this activity.
(d) Error Impact: Analyze how errors might affect overall conclusions drawn from the experiment.
(e) Real-World Applications in Sports: Considering billiards (Refer to Figure 2), discuss how the results of this activity could aid in playing.
(f) Further Applications: Identify other sports or activities that utilize the reflection rules discovered in this experiment.
Illustrative Figures
Figure 1: A depiction of the incident and reflected rays with the normal line.
Figure 2: An example of how billiards utilizes the principles of reflection.