Key concepts:

1. visible light is radiant energy that moves in transverse waves;
2. the visible spectrum includes light with different wavelengths;
3. matter influences the path of light; and
4. radiant energy can be transformed into thermal, mechanical, and electrical energy.

Central Idea: Visible light is a form of radiant energy that can be seen and can interact in different ways when it contacts an object.

light energy

• Energy may take different forms, including radiant energy.
• Radiant energy that can be seen by the human eye is called visible light.
• The sun produces radiant energy. Many types of radiant energy cannot be seen.
• Light travels in transverse waves and does not need a medium through which to move.

WAVELENGTH & FREQUENCY

• Light waves are characterized by their wavelengths. A wavelength is the distance between any two corresponding points on successive waves (usually crest-to-crest or trough-to-trough).

• The wavelength can be measured from any point on a wave provided it is measured to the same point on the next wave
• Frequency is the number of waves passing a given point in a designated time. The greater the frequency, the greater the amount of energy

• The visible spectrum has a range of colors that are determined by wavelength.
  • The colors of the spectrum from the longest wavelength to the shortest wavelength are red, orange, yellow, green, blue, and violet (ROYGBV).
  • The sum of these colors is white light

• Light transfers radiant energy.
  • For example, energy radiated from the sun is transferred to Earth by light.
  • When this light is absorbed, it warms Earth’s land, air, and water and facilitates plant growth through the process of photosynthesis.
• Current technology also transforms light energy into mechanical and electrical energy; an example of this is the use of solar panels to produce electrical power

REFLECTION, refraction, transmission, absorbtion

• Light travels in straight paths until it hits an object, where it is reflected, refracted, transmitted, and/or absorbed.
• Examples of refraction, or bending of waves, include
  • refraction causing a setting sun to look flat
  • a spoon appearing to bend when immersed in a cup of water
  
  • a glass prism dispersing white light into its individual colors as the colors refract at different angles (as visible light exits the prism, it is refracted and separated into the visible spectrum).

Light can be reflected when light bounces off an object.

An example of this is light hitting a mirror

TRANSPARENT, TRANSLUCENT, OPAQUE

• Light passes through some materials easily (transparent materials), through some materials partially (translucent materials), and through some not at all (opaque materials). The relative terms transparent, translucent, and opaque indicate the amount of light that passes through an object.
  • Examples of transparent materials include clear glass, clear plastic food wrap, water, and air.
  • Examples of translucent materials include wax paper, frosted glass, thin fabrics, and some plastics..
  • Examples of opaque materials include metal, wood, bricks..