Ch 11 - Light: Shadows and Reflections7th Science
Luminous vs. Non-Luminous Objects
What is the fundamental physical distinction between a luminous object (like the Sun) and a non-luminous object (like the Moon)?
What is the fundamental physical distinction between a luminous object (like the Sun) and a non-luminous object (like the Moon)?
- Luminous: Objects that actively generate and emit their own light (e.g., the Sun, stars, a lit candle, fireflies).
- Non-Luminous: Objects that do not produce their own light. They only become visible because they reflect the light from a luminous source that falls upon them (e.g., the Moon, planets, mirrors, humans).
Prism Memory Hook
Luminous turns the Lights ON; Non-luminous just Nods (reflects).
Fireflies and Bioluminescence
How do fireflies naturally utilize light, and why is their population currently declining in natural habitats?
How do fireflies naturally utilize light, and why is their population currently declining in natural habitats?
- Function: Fireflies are seasonal insects that utilize natural bioluminescence (internal chemical light production) to communicate with each other and attract mates.
- Decline: Their numbers are rapidly decreasing due to an increase in artificial light pollution (which disrupts their signals), significant loss of forest habitat, and excessive human disturbance.
Prism Memory Hook
A premium mnemonic for this topic is available in the Prism App.
LED Lamps in Society
Why is the Indian government actively promoting the nationwide use of Light Emitting Diode (LED) lamps over traditional incandescent bulbs?
Why is the Indian government actively promoting the nationwide use of Light Emitting Diode (LED) lamps over traditional incandescent bulbs?
- Efficiency: LED lamps consume significantly less electrical power while being much brighter and longer-lasting than traditional bulbs.
- Environment: They are highly eco-friendly and reduce energy strain on the grid.
- Boundary Condition (Disposal): At the end of their lifespan, LEDs contain electronic components and must be properly recycled or disposed of safely, rather than simply being thrown into regular household garbage.
Prism Memory Hook
A premium mnemonic for this topic is available in the Prism App.
Also in this chapter
27 more cards to study in Prism
- 4Rectilinear Propagation of Light
- 5The Bent Pipe Experiment
- 6Visualizing Light Paths (Laser in Water)
- 7Transparent vs. Translucent vs. Opaque
- 8Conditions for Shadow Formation
- 9Color of Shadows
- 10Dynamics of Shadow Size
- 11Shadow Length Throughout the Day
- 12High-Flying Birds and Shadows
- 13Multiple Light Sources and Shadows
- 14Object and Image Distance (Plane Mirror)
- 15Traditional Shadow Puppetry Across India
- 16Pinhole Camera Concept
- 17Constructing a Sliding Pinhole Camera
- 18Image Color in a Pinhole Camera
- 19Reflection of Light
- 20Visualizing Reflection (Comb Experiment)
- 21Properties of a Plane Mirror Image
- 22Lateral Inversion
- 23Sunlight Travel Time
- 24Symmetrical Letters in Mirrors
- 25Ambulance Lettering
- 26Plane Mirror vs. Pinhole Camera Images
- 27Small Mirror, Large Image
- 28The Periscope
- 29The Kaleidoscope
- 30Ancient Mirrors: Aranmula Kannadi
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7th Science
The remaining 27 cards of Ch 11 - Light: Shadows and Reflections are available in the Aspira Prism App with full interactive study tools, spaced repetition, and memory hooks.
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