Our eyes can see the sun light as white color even though its made of
a spectrum of colors. In vacuum as well as in air these colors travel
with the same speed so you can think of them as if they on top of each
other, and that is why we perceive sun light as white color( sunlight
really appears yellow for us because the blue and violet colors of the
spectrum scatter through the atmosphere and the rest of the colors shows
yellow). To see how colors can combine to one color then watch the
following videos:
We hope this exercise reminds you of a natural phenomenon that
shows the visible light spectrum. Indeed we enjoy the beautiful colors
of a rainbow in a sunny/rainy day. The water droplets separate the
light into its components, hence we see the visible spectrum of the
white light. Another way to separate light into a spectrum is by using a
spectrometer. In this case the light separates into a spectrum due to
an interference effect that results from a set of finely spaced lines
called a diffraction grating. As we shall see, studying spectra can be
very useful to identify elements because each element has its unique
spectrum. So spectrometers can be used to identify unknown elements.
However, we will use spectra to help us understand some properties of
atoms. First, we will build a spectrometer and use it to look at the
spectrum of different elements and materials.