Shadows and Penumbra
This experiment investigates the formation of shadows using different shadow rods. Light does not bend around the object, so a shadow of the same shape is cast on the screen.
What students learn
- Shadows are produced because light travels in straight lines
- A larger image is produced from a point source, due to diverging light rays from the single bulb
- Using the projecting lamp, which has a bulb at its focus and so gives a collimated beam, the shadow produced is similar in size to the object
The science behind this experiment
Shadows, umbra and penumbra. Shadows are formed when an object blocks the path of light. The shadow is the space behind the object where no light falls. Shadows have a shape similar to that of the object that produces them. We can get two types of shadows. A completely shaded area is known as umbra, whereas a partially shaded area is called penumbra.
A clear, distinct shadow is formed when the light source is smaller than the object so that all of the light is blocked.
Equipment used
- Inclined plane, with 3 different trackterminals — 5491.11
- Projector with 12V 20W halogen lamp — 4414.18
- Slider for projector — 4417.17
- Slider for holder — 4417.01
- White metal screen — 4418.35
Chemicals and reagents
Safety notes
Questions for students
- Why does the single bulb produce a larger shadow?
- Why does the projecting lamp produce a shadow similar in size to the object?
- Why is the shadow the same shape as the object?
- What is a solar eclipse?
What to expect
Disposal
Run this experiment in your classroom
This experiment is part of the ATP Mobile Lab — a self-contained laboratory that turns an ordinary classroom into a working science lab, with over 200 experiments in physics, chemistry, biology, robotics and engineering. Gali, the AI tutor built into ATP Connect, guides students through each step and answers their questions at the bench.
See the Mobile LabTalk to our team