Reflection of Light:

Objectives:

1.    Explain why white and black are not true colors.

2.    Describe how reflection of light affects an object's color.

3.    Describe why light reflects absorbs or light of a particular color.

Resources:

Notes:

The visible light spectrum consists of the colors red, orange, yellow, green, blue, and violet.  Although there are other wavelengths of electromagnetic radiation around us all the time, these are the only wavelengths we perceive as color.  When we mix all of them together we perceive the light as white and when we take them all away we perceive it as blackness.  Therefore we can say that:

• Black is not a color but the absence of color

• White is not a color but the combination of all colors

(ldt.stanford.edu/.../tita/mjrproj/ color/spectrum.gif)

It is important to understand that an object is only the color that it reflects.  It absorbs all other colors.  Therefore, the wavelength of light that determines the color of an object must be present in the light for the true color to be present. Things generally look different in candle-light because candles emit mostly red, orange and yellow.  Consider the image below.

This image is being hit by all of the visible light spectrum.  What would happen to the color if only part of the spectrum of visible light was used?

(www.bhs.berkeley.k12.ca.us/.../ color/images/cmyk_m.gif)

As you can see the images each reflect only the colors that are present in the light that they are hit with.  The reason for this is in the atoms.  All atoms have a natural frequency much like a tuning fork.  As light hits different atoms, the electrons vibrate and either retain the energy or emit the wavelength back as a photon.  The amount of the energy is called a quantum.

• Every atom has a natural frequency (quantum level) where it absorbs and releases light energy

• Most objects are made of many atoms, therefore, most things we see are a combination of colors.

For transparent objects, the color of the object is the color that it transmits.  The other colors are being absorbed.  The material in the glass that allows for selective absorption of color is called pigment.

(micro.magnet.fsu.edu/primer/ images/filters/dicroic.gif)