1. Collect all necessary equipment and plug in the light source (or ray box) into the DC transformer and then the transformer into a power point. 2. Set the power tuner to 12 volts (maximum) and place at one end of the desk with the bulb facing inwards. 3. Place the ruler directly in front of the light source so that one end (marked 0cm) is almost in line with the light bulb. This is so that the centimetre markings on the ruler are the actual distance from the light source. Macintosh HD:Users:160161:Desktop:Photo on 5-02-2014 at 2.41 pm
4. Attach the USB link to the light sensor (as shown in the image on the right) and then plug the USB link into the laptop. 5. Open Data Studio on your laptop, making sure that the connection between the application and the light sensor is strong. Once done, press the sunlight button on the light sensor and hold until it turns yellow. 6. Slide the white cardboard sheet into the back of the light source and shut the flaps on the sides so that light escaping out the back and sides is minimized. Make sure all other lights have been turned off and natural light has been minimized as well, making sure it stays the same for all trials.
7. Place the wooden block next to the 10cm mark on the ruler, ensuring that it is directly in line with the front side of the light source. Macintosh HD:Users:160161:Desktop:Photo on 5-02-2014 at 2.40 pm 8. Set the light sensor on top of the block ensuring that the front nozzle faces towards the light source and the tip is also in line with the 10cm mark on the ruler. Complete a few pre-tests to ensure that everything is working smoothly.
9. Press and hold the start button on data studio for 60 seconds and record the highest reading that appears in the data box. Record this reading in your table as a valid trial for the distance of 10cm. 10. Repeat the above step twice, ensuring that only the highest reading is recorded for each of the two remaining trials. Ensure that the control variables are the same as they were for the trial before with outside interference minimized so that the illuminated light measurements (the dependent variable) are as accurate as possible. 11. Move on to the next distance (20cm) and repeat steps 7-10, ensuring that the light sensor is at the new measurement. Once done, repeat 7-10 for the remaining eight distances and record data in table.
12. Once finished, eject the USB link from the laptop, save data on data studio and return equipment. 13. Write up report, ensuring to include a graph and results table. Our results show a wide range of relationships between the data. For instance, the shape of our graph shows an inverse relationship between light intensity and distance. The power trend line displays this relationship as it shows that as the distance increase, the light intensity decreases through its angular line curving downwards from left to right. The graph also suggests that if further distances were to be measured, the trend in decreasing readings will continue, as so far there has been no change in the inverse relationship.
There was no real pattern in the decreasing rate of light intensity against distance as the power trend line on the graph displays different gradients between points (i.e. the gradient between 10-20cm is much greater than that between 80-90cm). This is backed up by the fact that the equation formulated for the data- y=161484x-1.1661- which, although is a non-linear equation/relationship, it is complex and does not suggest a definite pattern and would most likely change if another distance was added. The data looks fairly reliable, as there are no anomalies, although the equation formulated does not match with the inverse square law (mentioned in conclusion), suggesting minor inaccuracy in data.
In conclusion, the results gathered are sufficient and clearly show that the distance an object is placed away from a light source does have an effect on the intensity of light (or illuminance) hitting a specific object. Furthermore, the data also allows for us to establish the relationship that the further the distance, the lower the illuminance. This convincingly answers our research question and proves my hypothesis correct/valid as the 10cm distance trials proved to obtain the highest light intensity (as hypothesized) at an average of 2614.33 Lux and the lowest readings were detected at the 100cm distance. Also, at each trial the readings were lower than those measured in all of the distances shorter than it. This is backed up by the sufficient data plotted on the graph that shows a steady decline in LUX measurements from 2613.33lux to 56.88lux.
The relationship between light intensity and distance occurs because light waves are emitted evenly in straight lines, they illuminate a specific area and as they travel further, they spread out and get less concentrated as the same amount of light has to cover more area, therefore decreasing the intensity of light. As a result, the brightness is also decreased, making the light look dimmer. This theory is the base principle for the inverse square law, which is a law in physics that can be used to find the intensity of light at any given distance by using the above knowledge.
The law states that the intensity of light at a given point equals the inverse of the distance squared multiplied by the original intensity of light at source (shown in figure 1). For example, if the distance is two units the light intensity will be one fourth of the original intensity, as the concentration of light would have decreased, as more area would be there to cover. (Britannica, 2005) Macintosh HD:Users:160161:Desktop:Screen Shot 2014-02-19 at 9.30.52 pm.png
Our experiment went quite well and we were able to collect all the necessary readings required, encountering very few problems during the experiment and were able to conduct three trials for each distance, thus improving the reliability of our data and deeming the experiment fair and valid. We had a sufficient sample size of ten different distances at equal intervals of 10cm-adequete for this experiment.
The extensive range of data collected allowed us to obtain an accurate trend line and formulate justifiable conclusions. Using our results, we were able to answer our research question in the affirmative that the distance of an object from a light source does affect the light intensity or illumines hitting the object, with the relationship being that an increase in distance equates to a decrease in light intensity.
The only major problem that we encountered and could have affected the reliability of our data was that we were unable to completely block out the background light coming in through the windows. Although one of the control variables was that all background light would be controlled and minimized largely, we were unable to compile with this as the blinds still let majority of the sun light in.
We also did not account for the light emitted from the light bulbs used by other groups during their trials- illuminated light that was potentially detected by our light sensor. We attempted to solve this problem by using sheets of paper to make a rectangular dome around the set up. This somewhat controlled the impact of background light, however it was not able to completely as the paper was only able to dim and reduce the intensity of light passing through into the set up and consequently, to the light sensor. This problem had a minor affect on the reliability of our data, although not enough to determine the test invalid, as we were still able to establish a relationship between distance and light intensity with reasonably accurate data that was otherwise reliable as no other problems were experienced.
Our method was fairly clear, concise and allowed us collect our data in a fairly orderly way, doing so for most tests. It allowed us to complete the experiment with accuracy excluding the human errors present that occur in most experiments and the major problem (mentioned above) that were inevitable based on the way the experiment was conducted. Although our method and experimental plan were quite accurate, easy to understand and allowed us to achieve our target of determining a relationship through a small-scale experiment, there are still many improvements that could be made to it to improve the validity of our results and further experiments could be carried out to extend this investigation.