Student Activity
OISE – University of Toronto
Objectives
· Explore and observe how curved mirrors produce real and virtual images
· Compare and contrast concave and convex mirrors
· Discover what the focal point of a mirror is
Ministry Curriculum Expectations
E2.1 use appropriate terminology related to light and optics, including, but not limited to: angle of incidence, angle of reflection, angle of refraction, focal point, luminescence, magnification, mirage, and virtual image
E2.3 predict the qualitative characteristics of images formed by plane and curved mirrors (e.g., location, relative distance, orientation, and size in plane mirrors; location, orientation, size, type in curved mirrors), test their predictions through inquiry, and summarize their findings
E3.3 describe, on the basis of observation, the characteristics and positions of images formed by plane and curved mirrors (e.g., location, orientation, size, type), with the aid of ray diagrams and algebraic equations, where appropriate
E3.5 describe the characteristics and positions of images formed by converging lenses (e.g., orientation, size, type), with the aid of ray diagrams
Background
This student-centered activity should be undertaken during this unit after the students have been introduced to the Law of Reflection, curved mirrors, and Ray diagrams. The interactive nature of this Gizmo should help students observe and modify the following: (1) when light rays hit a concave mirror, light farther from the central axis is reflected at greater angles than light near the central axis, resulting in convergence of light rays at a single focal point. The opposite occurs when parallel rays hit a convex mirror à the light rays diverge away from a single point located on the opposite side of the mirror; (2) when an object that emits light is placed to the left of a concave mirror, the light rays are focused to create an inverted real image. If the object is between the focal point and the mirror, an upright virtual image appears to be behind the mirror; (3) when an object is placed to the left of a convex mirror, the diverging reflected rays form an upright virtual image that is always smaller than the object because the object-focal point distance is greater than the focal length of the mirror.
Time recommendations: 20-30 minutes
Materials· Desktop or lap-top computers with access to ExploreLearning.com
Safety Precautions
· Nothing specific
Preparation
· Ensure classroom internet access; ensure access to ExploreLearning.com; review Gizmo prior to class
· Assign students to computers. Students can work individually or in small groups. Have students work through the activities in the Student Exploration, using the Gizmo. Alternatively, you can use a projector and do the Exploration as a teacher-led activity.
Demonstration Suggestions
· See preparation above
Answer Key
Questions:
1a. Approximately the same
1b. Upside down (inverted)
2a. Real image gets smaller, moves right and closer to central axis
2b. Real image gets larger, moves left and further from the central axis
2c. Real image gets larger, moves left and further from the central axis
2d. Real image gets smaller, moves right, and closer to central axis
3a. Real image gets smaller, moves right, and closer to the central axis
3b. Real image gets larger, moves left, and further from the central axis
4. The image is on the opposite side of the concave mirror, is upright, and larger than bulb (virtual)
5a. They never meet/cross at a point (they diverge)
5b. Virtual image since the image appears to originate behind the mirror (if reflected lines are extrapolated onto the opposite side of mirror, they do meet at a focal point
5c. The virtual image is always smaller than the bulb
6a. A concave mirror – a hot dog can be placed at the point where reflected light rays meet/converge
6b. A convex mirror – although the objects appear smaller, more objects can be seen and a larger area can be viewed because of the diverging nature of the reflected light rays
Limitations & Modifications
· Dependent on computer availability and classroom internet access
· See Teacher-Led alternative in Preparation (above)
Sources
“Ray Tracing (Mirrors)” Web. 12 Feb 2012: http://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=592
"Science." Ministry of Education / Ministère De L'Éducation. Web. 12 Feb. 2012.
http://www.edu.gov.on.ca/eng/curriculum/secondary/science910_2008.pdf