At Bodhiclasses, we nurture scientific curiosity through engaging lessons and detailed insights. Whether you’re a student aiming to master concepts or a teacher looking for ready-to-use resources, we’re here to simplify science and make it exciting. Today, let’s dive deep into Chapter 11 of Class 7 Science — a fascinating journey into Light: Shadows and Reflections.
🟡 1. Sources of Light
The chapter begins by differentiating natural and artificial sources of light. The Sun, stars, lightning, and some animals like fireflies are natural luminous sources. Artificial sources include electric bulbs, candles, oil lamps, and the modern LEDs.
Key Terms:
- Luminous objects: Emit their own light.
- Non-luminous objects: Do not emit light but reflect it (e.g. Moon).
🔸 Did you know? The government promotes LED lights as they are energy-efficient and environmentally friendly.
📏 2. Light Travels in a Straight Line
Through practical activities like aligning holes in matchboxes or peering through pipes, the concept that light travels in straight lines is demonstrated. It explains why shadows are formed and how we can predict their direction.
Activities:
- Matchbox torch experiment
- Candle flame through a bent pipe
📝 Observation: Light doesn’t bend around corners, and that’s why shadows are sharp when the path is blocked.
🌕 3. Transparent, Translucent, and Opaque Materials
This part explores how different materials interact with light:
- Transparent: Allow almost all light to pass (e.g., glass).
- Translucent: Allow partial light (e.g., tracing paper).
- Opaque: Do not allow any light (e.g., cardboard).
Children predict and then observe how a beam of light behaves when these materials are placed in its path.
🔎 Real-World Connection: Why can we see through windows but not walls?
🕶️ 4. Shadow Formation
A shadow forms when an opaque object blocks light. This section emphasizes:
- The need for a light source, an opaque object, and a screen.
- Translucent objects form lighter shadows, while opaque objects form darker shadows.
- Transparent objects may form faint or no shadows.
Concepts Explored:
- Size and shape of shadows
- Dependency on the distance between object, light, and screen
🎭 Cultural Note: Shadow puppetry has been an ancient form of storytelling in India (e.g., Tholu Bommalata, Ravana Chhaya).
🔁 5. Reflection of Light
Reflection is the bouncing back of light from a surface. Using mirrors and steel plates, students learn how light reflects and changes direction.
Terms Explained:
- Reflection: Redirection of light from a surface
- Plane mirror: A flat mirror that reflects light in a predictable manner
💡 Activity: Redirecting sunlight using a mirror to brighten dark areas.
🪞 6. Images Formed by Plane Mirrors
This section explores the images formed by mirrors:
- Erect and of same size as the object
- Laterally inverted (left becomes right and vice versa)
- Virtual (cannot be captured on a screen)
- The distance of the image from the mirror equals the object’s distance
Example: Why ‘AMBULANCE’ is written in reverse on emergency vehicles.
📷 7. Pinhole Camera
A pinhole camera is a device that forms a real and inverted image on a screen. It works without a lens, just using a tiny hole and a screen. Students learn:
- How to build one using cardboard boxes
- How light travels in straight lines to form an image
🧠 Insight: Unlike mirrors, pinhole cameras do not cause lateral inversion but they do invert the image vertically.
🧪 8. Periscope and Kaleidoscope
These fascinating tools are examples of real-world applications of light reflection:
Periscope:
- Uses two mirrors placed at 45° angles
- Helps see over or around obstacles (used in submarines and bunkers)
Kaleidoscope:
- Uses three mirrors arranged in a triangle
- Produces endless symmetrical patterns through multiple reflections
🎨 Artists and designers often use kaleidoscopes for creative inspiration.
🧠 Conceptual Learning through Activities
Every section is supported by hands-on experiments and explorations. The emphasis is not just on learning definitions, but on observing and experiencing light-related phenomena.
Concepts Reinforced:
- Light moves in straight lines
- Shadows depend on object and light position
- Mirrors reflect light and form images
- Different materials interact uniquely with light
📝 Final Thoughts
Light: Shadows and Reflections is more than a science topic—it’s a journey into understanding how we see, how mirrors work, and how shadows form. Through real-life applications and fun experiments, this chapter builds a strong foundation for future studies in physics and optics.
For learners, the takeaway is clear: Light is not just a source of vision; it’s a tool of discovery.
