Spectrum of a Fluorescent Light Bulb vs. Spectrum of the Sun
A comparison of the spectrum of the Sun (top half of the graphic) to the spectrum of a fluorescent light bulb (bottom half of the graphic). The two spectra are distinctly different: The spectrum of sunlight is shown as a continuous curve and rainbow. The spectrum of the light bulb consists of a set of discrete sections, shown as peaks on the graph and bands of color in the picture.
Top Half: Continuous Emission Spectrum of the Sun
On the left, the Sun is illustrated as a bright, solid white circle surrounded by semi-transparent rings of white.
On the right is a graph of brightness on the vertical y-axis versus wavelength in nanometers on the horizontal x-axis. The y-axis has an arrow pointing upward to indicate that brightness increases from the bottom to the top of the graph. There are no numbers, units, or tick marks on the y-axis. The x-axis ranges from 350 nanometers at the origin to 750 nanometers at the far-right end, with labeled tick marks every 100 nanometers.
The curve representing the continuous spectrum of sunlight is concave down with a shape resembling the top front part of a whale as seen from the side: The curve begins about halfway up the y-axis and continues upward with a concave down shape to a broad peak at the top of the graph at about 450 nanometers. It then decreases gradually to the right, leveling out at about 700 nanometers. There are no sharp peaks or valleys superimposed on the overall shape of this curve. (The detailed absorption features of the solar spectrum are not shown.)
Below the graph of the solar spectrum is a picture of the spectrum in the form of a long horizontal bar with rainbow coloring aligned with x-axis of the graph above. The rainbow ranges from purple on the far left to red on the far right. The rainbow is continuous, with no black lines or missing segments.
Bottom Half: Emission Spectrum of a Fluorescent Light Bulb
On the right is a simple illustration of a solid white spiral-shaped fluorescent light bulb.
On the left is a graph of brightness versus wavelength in nanometers. The scale and labels are the same as the graph showing the solar spectrum: Brightness increases from the bottom to the top. Wavelength ranges from 350 nanometers at the origin to 750 nanometers at the far right.
The spectrum of the light bulb consists of nine distinct peaks of different height and width, with no overall trend. From left to right the peaks appear at roughly: 405, 435, 490, 550, 580, 610, 630, 650, and 710 nanometers. The highest peaks are at 550 and 610 nanometers.
Below the graph is a picture of the emission spectrum in the form of a long horizontal bar aligned with the x-axis of the graph. Unlike the continuous rainbow of sunlight, this picture shows a series of discrete bands of color, separated by bands of black. The color bands correspond to the peaks on the graph. From left to right (shortest to longest wavelength) they are: purple, purplish blue, blue, greenish-yellow, yellow, yellow-orange, orange, orange-red, and red.
