Artificial Lighting Science Project Idea

Science project idea on the cost of artificial lighting.

Artificial Lighting- Science Project Idea

Cost of artificial lighting of rooms.Name the various methods of producing light for the illumination of rooms when sunlight is not available.We are especially concerned with the comparative costs of these different kinds of lights.To determine this, we must be able to measure the intensity of a light.To do this we must know how the intensity of a light decreases as the distance from the light increases.This may be found out by the following experiment.

Lighting Science Experiment I

Darken a room except for one small source of light.Arrange pieces of opaque cardboard respectively 1, 2, and 3 inches square, on supports so that they can be moved away from or toward the source of light.Place the 1-inch screen one foot from the light and place the second screen so that the shadow cast by the first just covers it.

In the same way place the third screen so that it is just covered by the shadow.Measure the distances between the first and second and the second and third screens.What is the relation of these distances to the distance between the source of light and the first screen?

If the first screen is removed it is evident that the light striking the second screen is the same that illuminated the first screen.But what is the area of the second screen as compared with the first?What, therefore, will be the intensity or brightness of the light on the second screen as compared with the intensity on the first screen?

In the same way compare the intensity of the light upon the third screen with that on the first screen.What conclusion can you draw now concerning the decrease of brightness or intensity of light as the distance from the source of light increases?

Your conclusion may be stated in the following terms: The intensity of light is inversely proportional to the square of the distance from the light-giving body.

This experiment may be modified by substituting for the first screen a larger screen in which is cut an opening one inch square.In this modification of the experiment the light giving body should be surrounded by an opaque screen in which a small pinhole has been made so that the light comes from a point.Unless the opening is very small the result will not be satisfactory.

The principle which we have discovered in the preceding experiment may be used hi the following way to com- pare the relative light-giving power of two lights.

Lighting Science Experiment II

Place the lights to be tested several feet apart on a table in a room which is otherwise dark.Slide an upright piece of opaque cardboard along between the lights until no shadow is cast on either side of the cardboard.This means, of course, that there is an equal illumination of each side of the cardboard.Since the intensity of light is inversely proportional to the square of the distance from the light-giving body, the relative power of the two lights may be calculated.If, for example, it is found that one of the lights is 4 times as far from the cardboard as the other (6), then a:6::4 2 :l 2 , or as 16:1.

The standard of measurement of the light-giving power of a light is called a candle power.This was originally the light given by a candle made according to certain specifications.At the present time the value of the candle power in the United States is established by a set of standard incandescent lamps maintained in the Bureau of Standards in Washington.Most incandescent lamps have the candle power etched upon them.It can be seen that if the candle power of one light is known the candle power of another lamp may be determined by the experiment above.

Knowing the light- giving power of two lamps, it is possible by finding how rapidly the oil or gas is consumed or the number of kilowatt hoursof electricity used, and the price charged, to estimate the cost per candle power of various kinds of lights.

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