Light 13 - Color - Absorbance vs Emitance default

Summary

This video explains the science of color perception, focusing on how light interacts with objects to create the colors we see. It covers the process of light reflection and absorption, where objects reflect specific wavelengths, and how electronic transitions in atoms affect the colors emitted or absorbed. The video highlights how colors arise from electron orbital changes, explaining why an object may look different when reflecting versus emitting light. The concept of light intensity and photon absorption is explored, showing how these factors influence our perception of color.

Takeaways

• 😀 Light is perceived through its interaction with objects, which either reflect, absorb, or emit light, resulting in the colors we see.
• 😀 The visible light spectrum ranges from violet (400 nm) to red (750 nm), and the intensity of light corresponds to the number of photons at each wavelength.
• 😀 A white object reflects all visible wavelengths, while colored objects absorb certain wavelengths and reflect the rest, creating their specific color.
• 😀 The energy levels of electrons in atoms determine which wavelengths of light are absorbed or reflected, leading to the color we perceive.
• 😀 When light strikes an object, some wavelengths are absorbed, and others are reflected. For example, a green object absorbs red and blue light, reflecting only green.
• 😀 An object that appears green does not have any electron orbital transitions that correspond to green light. Instead, it reflects green while absorbing other wavelengths.
• 😀 If an object only reflects certain wavelengths (e.g., blue light), the absorbed light results in a mixture of colors that we perceive depending on the material's energy levels.
• 😀 The process of absorption and emission of light involves electrons moving between energy levels. After absorbing energy, electrons emit light in all directions, reducing the intensity of the reflected color.
• 😀 Emitting light (e.g., in a gas discharge tube) produces a specific spectrum of colors (such as green and red), while reflecting light involves a broader spectrum.
• 😀 When mixing colors in paint, a small amount of one color added to another results in a slight change, similar to how absorbed and reflected light influences the color we see.

Q & A

What is the visual spectrum of light?

The visual spectrum of light is the range of wavelengths that the human eye can detect, typically from around 400 nanometers (purple-blue) to about 750 nanometers (red), with colors like green, yellow, and others in between.

How do we perceive colors when light hits an object?

When light hits an object, some wavelengths of light are absorbed, and others are reflected. The color we perceive is based on the wavelengths that are reflected, with the rest being absorbed by the object.

What happens when an object appears green?

If an object looks green, it reflects the green wavelengths of light while absorbing others, like red and blue. The electrons in the object's orbitals are tuned to absorb those wavelengths, and green is the only color that gets reflected.

Why can't a green object emit green light?

A green object can't emit green light because its electron energy levels don't match the energy required to produce green photons. Instead, it only reflects green light.

What is the difference between absorption and reflection in the context of color perception?

Absorption occurs when an object’s electrons absorb certain wavelengths of light, preventing them from being reflected. Reflection happens when light bounces off the object, with the reflected wavelengths determining the color we see.

How does an object that emits light, like a neon sign, produce its color?

An object that emits light, such as a neon sign, produces color by exciting electrons to higher energy levels. When the electrons fall back to lower energy levels, they release light in specific wavelengths, creating visible colors like red or green.

Why does the intensity of emitted light appear weaker compared to reflected light?

When light is emitted by an object, the photons are scattered in all directions, leading to a weaker intensity of light in the direction of the viewer. In contrast, reflected light retains its intensity as it bounces off the surface.

What role do electron orbitals play in determining the color of an object?

Electron orbitals play a crucial role in determining the color of an object because the energy levels of the orbitals dictate which wavelengths of light can be absorbed or reflected. Only wavelengths that match the energy differences between orbitals will be absorbed.

What is the relationship between the intensity of light and the number of photons?

The intensity of light is proportional to the number of photons at a given wavelength. More photons result in higher intensity, while fewer photons lead to lower intensity.

Why does white light appear when all wavelengths are reflected?

White light appears when all wavelengths of visible light are reflected equally by an object. This includes a mixture of red, green, blue, and other colors, which our eyes interpret as white.