The purpose of this lab was to explore the actions of light as it moves through a lens. A light source was used to project a real image through a magnifying glass and on to a white board to view how the light was refracted and altered.
Method and Results:
A magnifying glass was chosen and this glass was measured for its focal point. The method for the measurement was to use the suns light to focus a light rays onto the ground. Due to the magnifying glass being a convex lens it is know that the point at which the light is focused through it from a far off object is at the focal point. Three measurements were taken from the focal point on the ground to the lens. These measurements were taken for an average and to determine the uncertainty of the method.
f1= 14.10 cm
f2= 15.80 cm
f3= 15.00 cm
favg= 14.97 cm +/- 1.70 cm
The magnifying glass was set up distances from the light source of known multiples of the average focal length. A white board was placed behind the lens and adjusted in tell the image was focused. The distance from the lens to the white board was measured as was the height of the real image.
| Relative to f | Object distance (cm) | Image distance (cm) | Object height (cm) | Image height (cm) | M | Type of image |
| 5f | 74.85 | 23.5 | 3 | 1.30 | 0.433 | inverted/reversed |
| 4f | 59.88 | 24.5 | 3 | 1.75 | 0.5833 | inverted/reversed |
| 3f | 44.91 | 28.7 | 3 | 1.95 | 0.65 | inverted/reversed |
| 2f | 29.94 | 44.5 | 3 | 5.20 | 1.733 | inverted/reversed |
| 1.5f | 22.46 | 332.5 | 3 | 53.60 | 17.867 | inverted/reversed |
A measurement was taken at distance 0.5f but the image could not be focused. The object and image distance were graphed and an inverse relationship was found.
The inverse of both values was then taken and a linear relationship was discovered.
The absolute value of the slope of the graph is 0.7738 which is a value that is off from the expected value of one as this is the value of n in air. this discrepancy could be explained by the large uncertainty involved in our measurement of the focal point as the uncertainty of 1.70 cm is a large value. More likely though the % error of 22.6% is due to the low number of points measured and the arbitrary nature in which the focused real image was obtained. These cupeled with the fact that there was not an adequate light experiment setup lead to much uncertainty.
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