6A60.31: Projected Arrow with Lens
Description: This demonstration uses an optical bench with two arrows as the light source.
Using different lenses you can illustrate lens optics.
- Optical bench with Arrow source
- Opaque screen
- 200-300mm converging lens
- Other lenses if requested
- Include a meter stick and a 2m stick if measurement is desired.
- Turn the light upright.
- Place the opaque screen on the far end and place the desired lens in the middle.
- Test to make sure the light source works.
- When the professor is done, use caution as the light may be hot.
- When putting the optical bench away, you need not take the light off since the stand allows it to fold 90º on its side.
- Turn on the light source.
- Dim the lights in the classroom.
- Using the thin lens equation () and the focal length(F) of the lens,
you can show students that you can calculate where to place the screen for the image to be in focus. This requires you to measure the
- Make the object-lens distance between 1F and 2F to show an increase in magnification.
- Make the object-lens distance greater than 2F to show a decrease in magnification.
- Change the position of the lens to show that no image is formed when the object is 1F away from the lens.
- If the object is less than 1F away form the lens, no real image is produced (only virtual).
- For each image you can show if there is left-right and up-down reversal by comparing the direction of the arrows on the
screen to that of the source.