Light passing through a green filter appears green because the filter is designed to allow only the green portion of the light spectrum to transmit through it, while absorbing or blocking all other colors.
How Color Filters Work
Color filters function by selectively interacting with different wavelengths of light. White light, like sunlight, is composed of a spectrum of colors, each corresponding to a different wavelength. Color filters block certain wavelengths of light and let others pass through. This selective transmission is what determines the color we perceive after light passes through the filter.
The Specifics of a Green Filter
Following the principle of how color filters operate, a green filter has properties that specifically interact with the wavelengths associated with green light. For example, a green filter blocks all wavelengths except green light.
This means when white light (which contains red, orange, yellow, green, blue, indigo, and violet wavelengths) hits a green filter:
- Blocked Wavelengths: Wavelengths corresponding to red, orange, yellow, blue, indigo, and violet light are absorbed or reflected by the filter material.
- Passed Wavelengths: Only the wavelengths corresponding to green light are allowed to pass through.
The light that exits the filter is therefore predominantly composed of green wavelengths.
Why We See Green
Our eyes perceive color based on the wavelengths of light that reach them. When light composed mainly of green wavelengths enters our eyes, our brain interprets this as the color green. Thus, because a green filter transmits only green light, anything viewed through it, or any white light that passes through it, will appear green.
Here's a simple breakdown:
| Incoming Light Color (Wavelengths) | Green Filter Action | Outgoing Light Color (Wavelengths) | Perceived Color |
|---|---|---|---|
| White Light (All colors) | Blocks all except green | Green only | Green |
| Green Light (Green only) | Passes green | Green only | Green |
| Red Light (Red only) | Blocks red | None (Dark) | Black or Dark |
In summary, the appearance of green light after passing through a green filter is a direct result of the filter's property of selectively transmitting only the wavelengths associated with the color green.
