The Physics of Color

Characteristic of visual perception.

Color is a fundamental part of our daily lives, influencing everything from our mood to our choices. But have you ever stopped to wonder what color really is? In this unit, we will delve into the physics of color, exploring the visible spectrum, color perception, and the role of light in how we see color.

The Visible Spectrum and Color Perception

The colors we see are a small part of the electromagnetic spectrum, which ranges from radio waves to gamma rays. The visible spectrum, which our eyes can detect, ranges approximately from 400 nanometers (violet) to 700 nanometers (red). When light hits an object, the object absorbs some wavelengths and reflects others. The colors we see are the wavelengths that are reflected.

Absorption, Transmission, and Reflection of Color

When light encounters a material, it can be absorbed, transmitted, or reflected. Absorption occurs when the material takes in the light energy, often converting it to heat. Transmission is when light passes through a material without being absorbed. Reflection is when light bounces off a material. The color of an object is determined by the wavelengths of light it reflects. For example, a red apple appears red because it absorbs all colors except red, which it reflects.

Color Addition and Subtraction

Color addition involves combining colors of light, while color subtraction involves removing colors from white light. When red, green, and blue light (the primary colors of light) are combined, they produce white light. This is known as additive color mixing. On the other hand, color subtraction involves the removal of certain wavelengths from light, resulting in a color that is a mixture of the remaining wavelengths. This is how colored filters work.

Understanding Color Filters

Color filters work by absorbing certain colors (wavelengths) and transmitting others. A red filter, for example, absorbs all colors except red. It allows red light to pass through, which is why we see red when we look through a red filter.

The Role of Light Source in Color Perception

The color of the light source can significantly affect our perception of color. For instance, under a blue light, a red apple may appear black because the blue light doesn't contain any red light for the apple to reflect. Similarly, the color of an object can appear different under sunlight, fluorescent light, or incandescent light due to the different spectral compositions of these light sources.

In conclusion, the physics of color is a complex and fascinating subject, involving the interplay of light, matter, and our own perception. Understanding these principles can enrich our appreciation of the colorful world around us.