Light and Shadow - Q&A
Main Questions
1. What is bioluminescence? Give some examples.
Bioluminescence is the natural ability of living organisms to produce light through chemical reactions within their bodies. Examples: Fireflies, glow worms, jellyfish, and some deep-sea fishes.
2. What is a shadow? Write the three conditions necessary for the formation of a shadow.
A shadow is a dark region formed when an opaque object blocks the path of light.
Conditions for shadow formation:
1. A source of light.
2. An opaque object.
3. A screen on which the shadow can be formed.
3. What are the three types of lunar eclipses? How do they differ from each other?
The three types of lunar eclipses are:
1. Total Lunar Eclipse: The Moon passes completely into the Earth's umbra (dark shadow).
2. Partial Lunar Eclipse: Only a part of the Moon enters the Earth's umbra.
3. Penumbral Lunar Eclipse: The Moon passes through the Earth's penumbra, causing only a slight dimming.
4. What is an annular solar eclipse?
An annular solar eclipse occurs when the Moon is farther from the Earth and appears smaller than the Sun, so it covers the central part of the Sun, leaving a bright ring-like circle called the “ring of fire”.
5. Describe the working of a pinhole camera.
A pinhole camera works on the principle that light travels in straight lines. Light rays from an object pass through a tiny pinhole and form an inverted image on the screen inside the camera box. The smaller the pinhole, the sharper the image.
Exemplar Problems
1. Sometimes even when it is daytime, you can get complete black darkness in the sky, just like what you see at night. How is it possible?
This happens during a total solar eclipse, when the Moon completely covers the Sun, blocking its light and causing total darkness even during the day.
2. Suggest any one way to convert a transparent glass sheet into a translucent sheet.
By rubbing the glass with sandpaper or smearing it with oil, grease, or wax, the smooth surface becomes rough, scattering light and making it translucent.
3. The space beyond the Earth's atmosphere appears black. Explain.
Space appears black because there is no atmosphere to scatter sunlight. Without scattering, light travels straight and the sky looks dark even when sunlight is present.
