Class 6 - Light Shadows and Reflection

MCQs and Mock Test | NCERT - CBSE Curriculum

Prepare for exams with Class 6 Light MCQs and Mock Tests.
Covers reflection, refraction, shadows, eclipses, and pinhole camera questions.

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Quick Revision: Light

  • Light: A form of energy that produces the sensation of vision.
  • Speed of Light: 3 × 10⁸ m/s in air/vacuum; 2.25 × 10⁸ m/s in water; 2 × 10⁸ m/s in glass.
  • Luminous Bodies: Emit their own light (e.g., Sun, stars, firefly).
  • Non-Luminous Bodies: Become visible by reflecting light (e.g., Moon, book).
  • Transparent: Allows light to pass through easily (e.g., glass, air, water).
  • Translucent: Allows only part of light to pass (e.g., ground glass, tracing paper).
  • Opaque: Does not allow light to pass (e.g., wood, metals).
  • Rectilinear Propagation: Light travels in straight lines. Evidence: shadows, pinhole camera.
  • Pinhole Camera: Forms inverted, real images. Image size depends on distance of screen from pinhole.
  • Shadow: Dark patch formed when an opaque object obstructs light.
  • Umbra: Completely dark part of shadow where no light reaches.
  • Penumbra: Partially dark part where some light reaches.
  • Solar Eclipse: Occurs on a new moon day when the Moon comes between Sun and Earth.
  • Lunar Eclipse: Occurs on a full moon night when Earth comes between Sun and Moon.
  • Corona: Outer rim of the Sun visible during a total solar eclipse.
  • Diamond Ring: Ring of light during an annular solar eclipse.

Chapter Summary: Light

Light is a form of energy that enables us to see the world around us. It travels at an enormous speed of 3 × 10⁸ m/s in a vacuum or air, making it the fastest known phenomenon. Objects that emit their own light, such as the Sun, stars, and fireflies, are called luminous bodies. Objects that do not produce their own light, like the Moon, a book, or a chair, are non-luminous and become visible only when light from a luminous source reflects off them and reaches our eyes.

The behavior of light can be understood through its key properties. It travels in straight lines, a principle known as rectilinear propagation, which explains the formation of shadows and the working of a pinhole camera. A pinhole camera forms an inverted, real image, and its size depends on the distance between the pinhole and the screen. Materials are classified as transparent (allow light to pass easily), translucent (allow partial light), or opaque (block light entirely).

The interaction of light with objects leads to phenomena like shadows and eclipses. A shadow has two parts: the completely dark umbra and the partially dark penumbra. During a solar eclipse, the Moon casts its shadow on Earth, while during a lunar eclipse, the Earth casts its shadow on the Moon. Understanding these concepts helps us appreciate the nature of light and its role in our daily lives.

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