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Transcript

Under the Lights

Question

How does the intensity of a star change with distance?

Conclusion

In a galaxy far far away (aka my garage), my original hypothesis was: If a starlight's (light bulb) distance from the light meter is closer, then it will measure a greater intensity of brightness on a Lux light meter. The results of my experiment show that my hypothesis was indeed correct. My experiment shows that the intensity of the light bulb gradually decreases with distance. My results prove that a light bulb being measured from 5 ft has a much greater intensity than a light bulb being measured from 15 ft.

By: Erin Thomas

Prior Knowledge

•The purpose of my experiment is to determine if how far away a star is affects its intensity. Looking at the sky, a star apparent brightness looks greater from a closer distance. Since we can’t actually measure an actual star’s intensity, we can use a starlight model such as light bulbs of different wattage.

In this graph, it is evident that at a closer distance with the same wattage in all 3 trials a star or light bulb has a greater intensity. For instance, in trial 1 at 5 ft (60 watt) the light meter reads 26 Lux, but at 10 ft for the same trial it read 10 Lux. The light bulb's intensity decreased even more at 15 ft reading only 5 Lux. This was the same in the other two trials. In trial 2, the second 60 watt light bulb reads 28 Lux at 5 ft, 10 Lux at 10 ft, and 5 Lux at 15 ft. In trial 3, the third light bulb reads 25 Lux at 5 ft, 9 Lux at 10 ft, and 5 Lux at 15 ft. In conclusion, the intensity of the light bulb gradually decreased with distance.

Data

In this graph, it is evident that at a closer distance with the same wattage in all 3 trials a star or light bulb has a greater intensity. For instance, in trial 1 at 5 ft (75 watt) the light meter reads 34 Lux, but at 10 ft for the same trial it read 13 Lux. The light bulb's intensity decreased even more at 15 ft reading only 7 Lux. This was the same in the other two trials. In trial 2, the second 75 watt light bulb reads 35 Lux at 5 ft, 13 Lux at 10 ft, and 7 Lux at 15 ft. In trial 3, the third light bulb reads 31 Lux at 5 ft, 12 Lux at 10 ft, and 6 Lux at 15 ft. In conclusion, the intensity of the light bulb gradually decreased with distance.

This chart represents the average intensity of all trials. It supports my hypothesis that at a closer distance with the same wattage in all 3 trials a star or light bulb has a greater intensity. The average of trials for 40 w, at 5 ft the Lux meter reads an intensity of 17 Lux. At 10 ft it reads an intensity of 6 Lux, and an intensity of 3 Lux at 15 ft. The average of trials for 60 w, at 5 ft the Lux meter reads an intensity of 26 Lux. At 10 ft it reads an intensity of 10 Lux, and an intensity of 6 Lux at 15 ft. The average of trials for 75 w, at 5 ft the Lux meter reads an intensity of 33 Lux. At 10 ft it reads an intensity of 13 Lux, and an intensity of 7 Lux at 15 ft. In conclusion, the intensity of the light bulb gradually decreases with distance.

•The dependent variable is the intensity of the light bulb, which is what is being measured by a Lux meter.

The independent variables are:

How far away the star’s light (light bulb) is from the Lux meter (5 ft, 10 ft, or 15 ft)

The different wattage of light bulbs (40 watt, 60 watt, and 75 watt )

In this graph, it is evident that at a closer distance with the same wattage in all 3 trials a star or light bulb has a greater intensity. For instance, in trial 1 at 5 ft (40 watt) the light meter reads 18 Lux, but at 10 ft for the same trial it read 6 Lux. The light bulb's intensity decreased even more at 15 ft reading only 3 Lux. This was the same in the other two trials. In trial 2, the second 40 watt light bulb reads 16 Lux at 5 ft, 6 Lux at 10 ft, and 3 Lux at 15 ft. In trial 3, the third light bulb reads 18 Lux at 5 ft, 6 Lux at 10 ft, and 3 Lux at 15 ft. In conclusion, the intensity of the light bulb gradually decreased with distance.

When analyzing my data, I looked to see at which distance did the light bulb have the greatest intensity.

Analyzing Data:

no

If a starlight's distance from the light meter is closer, then it will have a greater intensity of brightness.

Hypothesis

The control is no light shining into the room for the light meter to read.

Materials

Procedure

  • 40 watt light bulbs
  • 60 watt light bulbs
  • 75 watt light bulb
  • Meter stick
  • Lux (light)meter
  • Tape
  • Zip ties
  • Camera
  • Music stand
  • Lamp post
  • Paper
  • Marker
  • Room with no light

• Clear an area or room so that no light is able to stream in.

• Set the starlight model by using the post of a lamp and zip tying the clamp lamp and new light bulb to it.•

• Next, measure the various distances needed on the floor of the room with a meter stick from the starlight model. (5ft, 10 ft, 15 ft) Mark each distance with tape and label it using a marker.

• Set up the Lux meter by zip tying it to a music stand.

• Set the first distance to 5 feet.

• Screw in the first light bulb, turn all the lights off in the room, and turn the first light bulb on.

• Next, turn on the Lux meter which measures the light bulb’s intensity. Press the hold button on the meter to hold result.

• Take a picture of the result on the light meter for the first light bulb from 5 ft.

• Repeat steps 5-8 for each distance and each wattage.

• Repeat steps 5-8 for each trial; having a total of 3 trials.

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