Convex Lens Mirror Imaging

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Light

Alternative titles: Convex Lens and Concave Mirror Imaging, Refractors and Reflectors Demonstration

Summary

This demonstration shows how convex lenses and concave mirrors can bend or reflect light rays to bring them to a focus and form real images on a screen.

Procedure

Place an object such as a candle, toy, or light source in front of a blank screen. Show that its light alone does not create a clear image on the screen.
Hold a convex lens between the object and the screen. Move the lens back and forth until a sharp, inverted image appears on the screen.
Replace the lens with a concave mirror, adjusting the distance between the mirror and the screen until the image comes into focus.
Compare the two methods: the lens refracts light to a focus, while the mirror reflects light to a focus.
Conclude by noting that telescopes use the same principles: refractors with lenses, reflectors with mirrors.

Links

image Formation by a Lens or Mirror - Jeff Regester:

Using a convex lens to produce a real image - Simon Lloyd:

📄 The Art of Projection: How Convex Lens Enhance Projectors - Science Simplified: https://explerify.com/the-art-of-projection-how-convex-lenses-enhance-projectors/

Variations

Try using different focal length lenses to see how image size and distance change.
Demonstrate with multiple objects at different distances to explore focusing limits.
Show how a magnifying glass (a convex lens) can project an image of a window scene onto paper.

Safety Precautions

Never use the lens or mirror to focus sunlight—it can cause eye injury or start a fire.
Handle glass lenses and mirrors carefully to avoid breakage and sharp edges.
Supervise younger students closely during demonstrations.

Questions to Consider

Why doesn’t light from an object form an image on a screen without a lens or mirror? (Because the rays spread out in all directions and do not converge to a focus.)
Why is the image formed by a convex lens or concave mirror inverted? (Light rays crossing at the focal point flip the image upside down.)
How do refracting and reflecting telescopes differ? (Refractors use lenses to bend light; reflectors use mirrors to focus light.)
Which type of telescope can be made larger in practice, and why? (Reflectors—large mirrors are easier to construct and support than very large lenses.)