Overview
The lecture explains why objects appear different colors based on the properties of visible light, how objects interact with light, and how color filters work.
The Visible Light Spectrum
- Visible light consists of a spectrum of colors from red (longest wavelength, lowest frequency) to violet (shortest wavelength, highest frequency).
- The order of colors can be remembered as ROYGBIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet).
- White light is a mixture of all visible wavelengths; black is the absence of light.
How Objects Appear Colored
- The color seen depends on the wavelengths of light hitting an object and the object’s properties.
- Objects appear colored based on the wavelengths they reflect, absorb, or transmit.
- Opaque objects do not transmit light—color is determined by reflected wavelengths.
- An object reflects certain wavelengths (e.g., blue objects reflect blue light, absorbing the rest).
- Some colors may result from the combination of reflected wavelengths (e.g., yellow may result from reflected red and green).
Transparent and Translucent Objects
- Transparent objects (e.g., window glass) transmit nearly all light, allowing clear visibility.
- Translucent objects transmit some light, with partial visibility through them.
- The color of translucent objects is determined by which wavelengths are transmitted most.
Color Filters
- Color filters allow only certain wavelengths to pass through, blocking others.
- Primary color filters transmit only red, green, or blue wavelengths.
- If white light passes through a green filter, only green wavelengths are seen.
- Viewing a blue object through a green filter results in black because blue light is blocked.
- Filters for non-primary colors (e.g., yellow) let through their color and primary colors that combine to form them (e.g., yellow filter lets through red and green).
Key Terms & Definitions
- Visible light — electromagnetic waves detectable by the human eye, arranged in a color spectrum.
- Opaque — material that does not let any light pass through.
- Transparent — material allowing almost all light to pass through.
- Translucent — material allowing some light to pass through but not enough for clear vision.
- Color filter — a material that transmits only specific wavelengths (colors) and absorbs the rest.
Action Items / Next Steps
- Review the color spectrum and memorization acronym (ROYGBIV).
- Experiment with color filters and different objects to observe color changes.