Light and Objects

Introduction

Objects are classified by what they do to light:
- Opaque: does not allow light to pass through; all light is either absorbed or reflected.
- Translucent: can be seen through, but not clearly; allows some light to go through, but some is also absorbed or reflected
- Transparent: allows almost all light to go through, so can be seen through clearly

All non-luminous objects which are colored appear so due to the fact that they absorb part of the incident radiation and reflect or transmit the remaining part to the observer; colors seen are those not absorbed.
Transparent colorless objects: transmit all wavelengths of the visible spectrum (no absorbance); water, glass.
Transparent colored objects: transmit only certain wavelengths of visible light and absorb the rest.
- The color seen from the other side of the object is the color of this object.
- Piece of red glass, when exposed to white light will transmit red and absorb all other colors.
Opaque white and black objects: they appear white when they mainly reflect all the wavelengths of visible light. (colorless when light is transmitted, white when it is reflected).
- Ideal black object: absorbs all visible light (opaque to visible light).
- Absorbed light converted mainly to heat.
- Grey object: partial absorbance and partial reflection of all frequencies of visible light.
Opaque colored objects: objects (opaque or transparent)) have their colors because they selectively absorb all other colors except their own (this is the only color that is left unabsorbed).
- When the light wave strikes an object, it interacts with that object’s electrons, and the greater mobility of electrons, the greater the degree of interaction.
- As a result, metals interact with light differently than non-metals.