Light Absorption, Reflection, and Transmission

What happens to a light wave when it hits a boundary or another medium?

How does this behavior contribute to how we perceive color?

Key Points

All substances/objects/materials are made of atoms.

These atoms always vibrate at a frequency that is substance-specific, which is called the natural frequency.

Absorption, Reflection, or Transmission?

When the incident light wave has the frequency identical to that of the atoms in the substance, the light wave will be absorbed.

Absorption → Vibration → Thermal Energy

Absorption, Reflection, or Transmission?

If the substance is transparent, the light wave will cause a temporary vibration in the particles as it passes through.

It would then issue out of the material on the opposite end.

Reflected

Absorbed

Transmitted

Absorption, Reflection, or Transmission?

If the medium is opaque, then the light wave will cause a temporary vibration in the medium and be reflected back at an angle equal but opposite to the angle of incidence.

Law of Reflection

How does this relate to color?

We know that light from the sun comes in waves containing all of the colors of the rainbow.

We also know that every given substance cannot

absorb nor reflect all of those waves.

In a given substance, some of the waves are reflected, some are absorbed, and some are transmitted.

Example Problem

More Practice

Main Point

Color is NOT an inherent property.

Color is derived from HOW light “reacts” with certain substances.

Homework

• Take an article from the front and take out a blank sheet of paper.

• This article is also available as a link on EdModo.

• You must read this and write a well-structured 3-4 sentence conclusion of the findings of the article, including evidence provided therein.