Activity Description

Each animation in this sequence of two shows a point source which is located in front of a lens that is hidden behind a pink box. The point source can be dragged around and the transmitted rays viewed. Students view the transmitted rays and can deduce the type of optical element hidden behind the pink box.

Target Conceptual Difficulty

A convex lens can form both a real and a virtual Image.

PowerPoint

Working Backwards Task - Hidden Lenses (TurningPoint)

Working Backwards Task - Hidden Lenses (iClicker)

Simulations

Working Backwards Task - Hidden Lens #1

Working Backwards Task - Hidden Lens #2

Presentation Notes

To begin each simulation click on the Initialize link. Move the point source around. You want to make sure that you get both near and far away from both lenses. To reveal the hidden optical element click on the Answer link. (You may have to scroll down to see the link).

Student Results

Following their experience with the hidden mirror tasks, the students did very well on this task. For the first lens 72% initially identified the lens correctly as a concave lens. Following small group discussion 100% of the students correctly identified the lens as concave. For the convex lens 100% of the students correctly identified it as convex initially and no follow up small group discussion was held.

1.) What type of lens is behind the screen?
Responses (percent) (count)
Concave 72.73% 16
Convex 27.27% 6
Cannot be determined 0% 0
Totals 100% 22


2.) What type of lens is behind the screen?
Responses (percent) (count)
Concave 100% 22
Convex 0% 0
Cannot be determined 0% 0
Totals 100% 22


3.) What type of lens is behind the screen?
Responses (percent) (count)
Concave 0% 0
Convex 100% 22
Cannot be determined 0% 0
Totals 100% 22

Pen and Paper Actvivities

Pen and Paper version for activty #1

Pen and Paper version for actvity #2

Follow up tipers from homework assignments, test reviews and test items