Curved mirrors -Activity

Curved Mirrors & Convex Lens — Class 8 (ICSE)

Activity: Use mirrors and a convex lens to study reflection and refraction. Use a tree outside the window as the distant object.

Materials

• Concave mirror (small handheld)
• Convex mirror (small handheld / shaving-type)
• Convex lens (double convex, focal length suitable to form image of tree)
• White paper or cardboard screen
• Window with clear view of a distant tree
• Measuring tape / ruler, marker

Safety & Setup

Do not use direct sunlight focused on any flammable object. For this activity use a distant tree outside the window as the bright object — do not use mirrors to focus strong sunlight on skin or paper for long.

Activity Procedure (Step-by-Step)

1. Concave Mirror — Reflection (Real image)
   Place the concave mirror facing the classroom window so it receives light reflected from the tree (indirect daylight). Hold a white paper/screen in front of the mirror and slowly move it back and forth until an inverted image appears on the paper. Notice the sharp, real image when the screen is at the focus or beyond.
2. Convex Mirror — Reflection (Virtual image)
   Hold the convex mirror and stand so you can see your face. Observe that your image is erect, smaller and appears behind the mirror — this image is virtual and cannot be caught on a screen.
3. Convex Lens — Refraction (Real image of a tree)
   Hold the convex lens between the window and the paper. With the lens facing the distant tree, move the paper slowly behind the lens until an inverted, real image of the tree forms on the paper. Adjust the lens-to-screen distance to get a sharp image. This shows refraction and convergence of light through a transparent medium.
4. Compare
   Discuss differences: the mirror forms images by reflection (light bounces), the lens forms images by refraction (light passes through and bends).

Teacher Tips (EchoLearning)

• Ask one student to explain observation; have the class echo a short sentence (e.g., “Concave mirror — real inverted image!”).
• Encourage students to note where the image is formed: in front of the mirror/screen or behind the mirror.

Quick Diagrams

Concave mirror → real inverted image on screen (place screen in front)

Convex mirror → virtual erect diminished image (appears behind)

Convex lens → inverted real image of distant tree on paper

Question & Answer (Use for discussion / short test)

Q1. What phenomenon explains the image formed by concave and convex mirrors?

Reflection

Q2. Which device (mirror/lens) would you use to form a real image of a distant tree on a paper?

Convex lens (by refraction)

Q3. How is the image formed by a convex mirror different from that of a concave mirror (for a distant object)?

Convex mirror → virtual, erect, diminished; Concave (distant) → real, inverted, may be smaller

Q4. When the screen is placed where the concave mirror focuses light, what type of image is obtained?

Real and inverted image (can be projected on screen)

Q5. Why do we see an inverted image of the tree when using a convex lens?

Because rays from the distant tree converge and cross after passing through the lens, forming an inverted real image on the screen

Q6. Where does the virtual image appear to be when seen in a convex mirror?

Behind the mirror (cannot be caught on a screen)

Q7. Give one classroom safety rule for this experiment.

Do not focus strong sunlight on paper, skin, or flammable objects; use indirect daylight and the tree as object instead

Q8. Short practical: How would you find the focal length of the convex lens using the tree?

Focus the distant tree on a screen; the distance between lens and sharp image ≈ focal length (since object is effectively at infinity)

Prepared for Class 8 (ICSE) — Activity uses reflection (mirrors) & refraction (lens) with a tree as the distant object.