10 Questions
What happens when you look through a red cellophane?
Everything appears in a shade of red
What type of light does a green cellophane allow to pass through?
Green light only
What does it mean that red cellophane absorbs other colors of light?
It stops other colors of light from passing through
Why won't red light pass through a green cellophane?
Because green cellophane allows only green light
What is the general rule regarding color filters like glass or cellophane?
They only allow light of their own color to pass through
If you look through a blue cellophane, how will things appear?
In a shade of blue
Why does a green object appear black when viewed through a red cellophane?
"Red and green make black"
What would happen if you view an orange object through a blue cellophane?
"Orange and blue make black"
Why does a yellow object appear as its true color when viewed through a yellow cellophane?
"Yellow reflects yellow and absorbs the rest"
What is the reason behind why some objects appear black when viewed through certain color filters?
Because those objects absorb all colors except what the filter allows through
Study Notes
Optical Phenomena
- Optical phenomena are observable events resulting from the interaction of light with matter.
Rayleigh Scattering
- The blue color of the sky and the red color of sunsets are due to Rayleigh scattering.
- Gases and suspended dust particles in the atmosphere scatter shorter wavelengths of visible light (violet and blue) more than longer wavelengths (red).
- Our eyes are more sensitive to blue light, making the sky appear blue.
Color of the Sun
- The sun appears yellow during midday due to the direct passage of dominant amounts of yellow frequency.
- As the sun approaches the horizon, it becomes red due to the scattering of red light, the lowest frequency in the spectrum.
Clouds and Rain Clouds
- Water droplets in clouds are of similar size as the wavelength of sunlight, scattering all visible light and appearing white (Mie scattering).
- Rain clouds are dark due to their thickness and height, blocking sunlight and giving a gray color.
Rainbows, Halos, and Sun Dogs
- Rainbows are optical illusions, dependent on the position of the observer and the sun.
- Light is refracted as it enters the surface of a raindrop, creating the colors of the rainbow.
Mirages
- Inferior mirage: light bends upward due to warm air near the ground, creating an inverted image below the upright one.
- Superior mirage: light bends upward due to cold air near the ground, creating an inverted image above the upright one.
Light and Colors
- Artificial light has a different mixture of wavelengths than sunlight, affecting how colors appear.
- Incandescent bulbs heighten warm colors, fluorescent bulbs intensify blue and green, and CFLs produce a warm, neutral, or bluish light.
- LEDs have cooler or warmer lights, and "smart" LED bulbs can be controlled.
Sunlight and Room Lighting
- Sunlight changes throughout the day and is affected by a room's location.
- East-facing rooms have warm and yellow light before noon, bluish later in the afternoon.
- West-facing rooms produce shadows and make colors look dull.
- South-facing rooms bring out the best in cool and warm colors.
- North-facing rooms have cool and bluish light.
Color Filters
- Cellophane is a transparent material that changes the color of what is seen through it.
- Each color filter (e.g., red or green cellophane) allows only light of its own color to pass through and absorbs other colors.
Test your knowledge on various light phenomena such as different reflections on concave and convex sides, mirages, laser light passing through cellophane, and color appearances in different lighting conditions.
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