Light and Its Properties

Light

• Light and sound are crucial to our understanding and experience of the world.
• Light is needed to see objects and plants use it to produce food.
• Light from the sun is the primary energy source of our planet.
• The process of how objects are visible has been extensively studied.

Luminous and Non-luminous Objects

• Luminous objects emit their own light (e.g., the sun, stars, light bulbs).
• Non-luminous objects do not emit light; they become visible when light from a luminous source reflects off them (e.g., the moon, a table).
• Objects are visible only when light from them reaches your eyes.

Opaque, Transparent, and Translucent Objects

• Opaque objects do not allow light to pass through them like a steel tumbler.
• Transparent objects allow light to pass through them easily, like a glass tumbler.
• Translucent objects allow some light to pass through, but not enough to see objects clearly through them; like a tinted or milky glass tumbler.

Active Physics Experiments

• Experiments demonstrated how different types of materials interact with light.
• Objects like steel tumblers, glass tumblers, and tinted glass tumblers were used in experiments.

Rectilinear Propagation of Light

• Light travels in straight lines.
• This is known as rectilinear propagation.
• Shadows, eclipses, and images are formed due to this property of light.
• Light doesn't change direction unless it encounters a different medium or is disturbed

Speed of Light

• Light travels at an incredibly high speed in a vacuum: 300,000 km/s (or 3 x 10⁸ m/s).
• Its speed is slightly slower in other transparent materials like water or glass.

Properties of Light

• Light is a form of energy that travels in waves.
• Light spreads outwards from a source.
• Light can travel through empty space (vacuum).
• Light rays travel in straight lines.

Reflection of Light

• Reflection is the bouncing of light rays off a surface.
• The angle of incidence equals the angle of reflection.
• Light reflects off a surface in a predictable way, following the laws of reflection.
• The laws of reflection apply to both plane and curved surfaces.

Plane Mirrors

• Images formed by plane mirrors are virtual, upright, and laterally inverted.
• The image size equals the object size.
• The image distance equals the object distance from the mirror.
• The image is as far behind the mirror as the object is in front.

Numerical and Active Physics Examples

• Examples of calculations involving angles of incidence, reflection, and deviation are included.
• Experiments illustrating concepts like reflection from plane mirrors are described.

Regular vs. Diffuse Reflection

• Regular reflection occurs when light reflects off a smooth surface, such as a mirror. The reflected light rays remain parallel to each other.
• Diffuse reflection occurs when light reflects off a rough surface. The reflected rays scatter in many directions.

Light in Different Situations

• Examples of how light behaves in various situations, such as observing images through surfaces or viewing the sun from different times are discussed.