Light and matter
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Intros
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Examples
Lessons
- Give the reason why would you choose a window shade that is translucent or opaque.
- What color do you add to green light to obtain white light?
- What primary pigment colors must be mixed to get blue?
- What color will a yellow tennis ball appear when is illuminated by
- White light
- Green and red light
- Blue
- What would be the result of passing a beam of light through polarizing filter?
- Can sound waves be polarized?
Topic Notes
In this lesson, we will learn:
- Transmission of light through different materials
- Formation of spectrum of light
- Additive color process
- Colors by subtraction
- Formation of color by light, pigments, and dyes
- Polarization of light
Notes:
- Transparent materials: Transmit light waves without distorting images (glass, air)
- Translucent materials: Transmit light waves but objects can not be see clearly (frosted light bulbs)
- Opaque: Transmit NO light but absorbs and reflects all light incident upon them (wood, brick)
- Spectrum: When a narrow beam of light passes though a prism, rainbow of different colors can be seen
- Additive color process (RGB): The additive mixture of blue, green, and red light produces white light.
- Primary colors: red, green, blue
- Secondary colors: The primary colors are mixed by pairs to produce secondary colors;
- Yellow (red + green), Cyan (blue + green), Magenta (blue + red)
- Complementary colors: Secondary colors of light, when combined with the primary color, produces white light.
- Cyan is complementary to red
- Magenta is complementary to green
- Yellow is complementary to blue
Dye Vs. Pigment
- Dye: A molecule that absorbs certain wavelengths of light, and transmit or reflects others
- Example: Tomato is red because it reflects red and absorbs green and blue lights.
- Pigment: A colored material that absorbs a certain colors and transmits or reflects others. Pigment particles are larger than a molecule and can be seen with a microscope.
Primary Pigment Vs. Secondary Pigment
- Primary Pigment: A pigment that absorbs only ONE primary color from white light and reflects the other two. (yellow pigment absorbs blue and reflects green and red)
- Secondary Pigment: A pigment that absorbs TWO primary colors and reflects one. (red absorbs green and blue, green absorbs red and blue, blue absorbs red and green)
- Thin-film interference: Spectrum of colors produced by a soap bubble or by the oily film on water. Colors formation is the result of constructive and destructive interference of light waves.
- Polarization: Using polaroid material, the direction of vibrating light waves can be modified from many directions to ONLY one specific direction.
- Polarizer: The material through which light get polarized (polarizing filter)
