Overview
This lecture introduces the concept of light, explaining its nature as electromagnetic radiation, differences between luminous and non-luminous objects, and what happens when light interacts with surfaces.
Nature of Light
- Light is a form of energy known as electromagnetic radiation.
- It travels in waves and does not need a medium; it can move through a vacuum.
- Light moves incredibly fast, at about 300,000 km per second in a vacuum.
Luminous and Non-Luminous Objects
- Luminous objects produce and emit their own light (e.g. the Sun, light bulbs).
- Non-luminous objects do not produce light but can reflect light from luminous sources (e.g. the Moon, a book).
Interaction of Light with Surfaces
- When light hits a surface, it can be reflected, absorbed, or transmitted.
- Reflection occurs when light bounces off a surface, like a mirror.
- Absorption happens when light energy is taken in by the material, often turning into heat.
- Transmission is when light passes through a material, such as glass.
Key Terms & Definitions
- Electromagnetic radiation — energy that travels in waves and includes light, X-rays, and radio waves.
- Luminous — describes objects that generate and emit their own light.
- Non-luminous — describes objects that do not make light but may reflect it.
- Reflection — the bouncing of light off a surface.
- Absorption — the process where light energy is taken in by a material.
- Transmission — the passing of light through a material.
Action Items / Next Steps
- Review examples of luminous and non-luminous objects in your environment.
- Observe what happens when light interacts with different surfaces at home or school.