Light Reflection Lab
Grade Level/Subject
11th grade physics (Principles of Physics)
Unit
Optics
Enduring
Understanding
The angle of incidence equals the angle of reflection.
SOL Objectives
PH.3
The student will investigate and understand how to
demonstrate scientific reasoning and logic. Key concepts
include
e) construction and defense of a scientific viewpoint
(the nature of science).
PH.11 The student will investigate and understand, in describing
optical systems, how light behaves in the fundamental
processes of reflection, refraction, and image formation.
Key concepts include
a) application of the laws of reflection and refraction;
Title
Laser Targeting
Lesson Objective
Students will position mirrors in a manner that will direct a laser
beam to a specific target.
Inquiry Level
2 – The question and methods are provided but the solution
remains open.
Materials Required





low power laser
tripod
several small mirrors
mirror mounting system (mini camera tripods or tape
mirrors to whatever looks feasible)
target
1
Laser Targeting Lab
Background: Laser targeting is commonly thought of as an accurate way to direct missiles or bombs to a
specific target. However, it is also used for less destructive purposes, i.e. it is used in medical
procedures. For example, it is used in spinal surgery for directing where a machine should insert a drill
or needle. This is much more precise, and therefore safer, than is capable by a human. Whatever the
purpose, the main idea is that a laser beam is directed to an exact location (target).
Objective: You will use mirrors to direct a laser beam from its source to a designated target.
Rules:




You may not move the laser
You may not move the target
You may use any of the provided mirrors to reflect the beam to where you want it to go.
Your teacher must see the laser on your target.
NOTE: Intentionally directing the laser beam towards another person is potentially dangerous and will
not be tolerated.
Analysis
1. Why are mirrors required to make the laser light reach the target?
2. What did you have to do with a mirror if the light wasn’t going where you wanted it to go?
3. How does the angle that the light hits the mirror relate to the angle at which the light leaves the
mirror? (Test this with a protractor if it helps).
4. Summarize your findings in a statement that includes the phrases “angle of incidence” (the
angle at which the light hits the mirror) and “angle of reflection” (the angle at which the light
leaves the mirror).
2
Teacher Supplemental






This lab is intended for use in a Principles of Physics class. It would probably be difficult to do
with a large number of students. It may be a good idea to have one lab group doing this lab
while the other groups are doing a different activity. Ideally, the lab groups could rotate
through a few different labs for which sequence is irrelevant.
Tape edges of mirror if they are at all sharp.
Use small camera tripods as mirror mounts or tape them to ring stands
Demonstrate basic reflection with a laser pointer. This may seem obvious but will hopefully get
students thinking about the way that light is reflected.
Test your laser beforehand to get an idea about how many mirrors may successfully be used.
A green (532 nm) diode laser pointer may work best in bright conditions (although it is more
difficult to secure to a tripod).
3
Laser Target
C
B
A
B
Group Members: ________________________
__________________________
________________________
__________________________
________________________
__________________________
Teacher’s Initials: _______________
4
C