# Properties of Light

1260 words 6 pages
Danielle Silverstein
PHY 101 Section 10497
March 4, 2013

Light up this World

Purpose:

In this lab experiment, LED lights will be used to show how when E&M radiation is absorbed, the energy is converted to heat. A drop of isopropyl alcohol will absorb light energy of different colors, and the evaporation rate of the alcohol will be measured. The key to this lab is the evaporation rate is directly related to the energy of the light shining on the drop.

Materials: * * LEDs and circuits (from previous lab) * Pipette (or eyedropper) * Rubbing alcohol * Index card * 9-volt battery * Flashlight * Stopwatch * Small cardboard box (shoe box)

Procedures:

A three-sided enclosure from the cardboard box

The frequency of the light, which is the number of wavelengths per seconds is calculated using the equation C=LN. L is the wavelength, N is the frequency, and C is the speed of light (Library Thinking Quest).

From the observations collected, the red LED light took the longest to dry the drop of alcohol and the blue dried it the fastest. Since the red light is on the lower end of the electromagnetic spectrum is used the lowest amount of energy. Just by looking at the brightness of the light, this conclusion was made but reassured after doing some research. The red light was very dim and faint compared to the brightness of the green and the blue. The blue was the brightest of the lights. This light used the most energy and is one of the farthest on the spectrum beside violet. Since the frequency of light increases as the color of light moves down the spectrum, the red light has the smallest frequency of 4.42*10-14, green has middle frequency of 5.66*10-14 and blue has the largest frequency of 6.37*10-14. The frequency is directly proportional to the energy produced by each of the light, which is shown in the graph above. The blue light had the highest frequency and that used the most energy. The red LED used the least amount of energy because it had the lowest frequency. The greater the frequency caused the alcohol to dry faster since it used more heat (energy) at one time.

Light energy and frequency are

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