11 = 1 = 1 – 1 = 11 – 10 – 1 = V=110
V 10 11 110 110 110
12 = 1 = 1 - 1 = 6 - 5 = 1 = V = 60
V 10 12 60 60 60
13 = 1 = 1 - 1 = 13 - 10 = 3 = V = 43.3
V 10 13 130 130 130
14 = 1 = 1 - 1 = 7 - 5 = 2 = V = 35
V 10 14 70 70 70
15 = 1 = 1 - 1 = 3 - 2 = 1 = V = 30
V 10 15 30 30 30
Prediction shows that the closer the object /lens distance the longer the lens/image is and it is the opposite for the longer object/lens distance is the shorter the lens image is.
Equipment List
- Ruler
- Screen of thick white paper
- Photographic slide (as object)
- Lens (focal length of 10cm)
- Lens stand
- Clamp stand
- Power pack
- Ray box
Experiment Diagram
Plan
- Set up equipment and find focal length of lens.
- Measure out object/lens distance with a ruler.
- Three tests and measure lens/image distance.
- Do the same for 11,12,13,14,15 object lens distance three times each and measure lens/image distance.
- Pack away.
Method
I will set up my equipment as I have shown above in the diagram and then change the distance between the screen and the lens until the image projected on the screen is as clear as possible.
I will record the v value for each of the different u values. I will then repeat experiment three times in order to ensure accuracy.
Fair Testing
In order to ensure that my results are as accurate as possible, I will take care not to alter any of the control variables. I will conduct the experiment in a blacked-out room in order to give an accurate observation of the image. The same pupil in will observe the image every time to ensure accuracy, this is because people’s eyesight’s differ and may give different results. I will conduct the experiment three times to show up any anomalies that may occur.
Results
The following results are from our experiment:
These results suggest that there is a negative correlation between the length of u and the length of v. I think that these are fairly accurate results as they all show similar trends and they match nearly exactly with our predictions as show below.
I will now plot a graph showing the predicted results versus the actual results.
Conclusion
It is interesting to note that the difference between the predicted and actual results is greater the closer the object is to the lens. This is because the nearer you get to the lens; the more changes and inaccuracies affect the distance of the image of the image. It is because the angle of refraction becomes much steeper more easily at close ranges.
The reason for the negative correlation between the distance of the object from the lens and the distance of the image from it is that the lens must bend the rays of light.
Evaluation
Although I took care to blackout the room I was working in, the light intensity could still vary, both in the background light and also in the light source. I could use a darkroom and light sensors to measure the amounts of light at various points and to make sure that they are all zero. I could also use a sensor to measure the level of light emitted from the source and have a computer automatically adjust it so that the level is constant. A good quality bulb and a steady controlled power source would also be necessary to prevent varying light intensity from the source. Laser light could also be used and would be easier to measure and with computer instruments.
Despite this the chance for inaccuracies, the investigation turned up no anomalies and the quality of the evidence is good. But the experiment could be repeated with better equipment (mentioned above) and a wider range of lengths. I could also repeat the experiment varying the angle of the lens, and the focal length of the lens to see if they have an effect on the images produced and if so, what the effects are.
