Leanne Lansangan
2nd Tillay, Fiziks
2/28/11
Lab 15B Pasco Optics
Conclusion
Results:
The data collected for experiment 1, part 1 indicates that combining all three primary colors of
light results in white light. This was determined by using a ray box that produces red blue and
green lights and a convex lens. When the rays of light were shone through the lens and
reflected onto a white piece of paper, the rays combined to produce white light. For part 2 of
the experiment, the data indicates that the apparent colors of different colors of ink changes or
remains the same depending the various colors of light that are shone upon it. With the blue
light, the red ink line stayed red and the black line also stayed the same. However, with red
light, the black ink remained black while the blue ink appeared to be black. The lines changes its
apparent color depending on the light because the ink reflects and absorbs different light, For
example, red ink appears red because it reflects red light and absorbs other colors. The data
collected for experiment 2 shows that a single ray of light that is shone through a prism only
separates into colors at a certain angle. The angle of emerging ray must be the largest possible
to produce different colors of light. The colors that can be seen are : purple, blue, red, white,
and yellow are seen in order from left to right. The observations also shows that blue id
refracted at the largest angle and has the largest index of refraction. For experiment 3 part 1,
the data collected indicates that the angle of incidence and angle of reflection are equal. This is
also according to Snell’s law. For part 2 of the experiment, the data determines the relationship
between focal length and the radius of curvature of cylindrical mirrors. This was found by
measuring the focal length of a concave mirror and a convex mirror and measuring the radius of
curvature by using a compass. For the concave mirror, the focal length was 7 cm while the
measured radius was 14.7 cm. For the convex mirror, the focal length was 8.3 cm while the
measured radius was 16.9 cm. This shows that the radius of curvature is twice the focal length.
The data obtained for experiment 4 shows that the angle of incidence and angle of refraction
should be equal to each other. The indices of refraction are also measured using these angles.
For experiment 5, the data obtained shows that the greater the critical angle, the smaller the
index of refraction. For experiment 6, the data collected shows that if the outgoing rays of a
convex and concave lens are parallel, the focal lengths of the two lenses are opposites, but
equal in magnitude. The data in experiment 7 indicates that a plano-convex lens are either
converging or diverging depending on its surroundings. It is converged when section 1 was filled
with air while it diverged when section 1 was filled with water. The observations during
experiment 11 shows that the ray of light separates into colors at angle of 25 and the maximum
angle of refraction is 78 degrees.
Purposes:
The purposes of this lab was to understand the main concept of Snell’s Law, the relationship
between focal length and radius of curvature, how a prism separated white light into colors at
certain angle, how to calculate critical angles, and as well as to calculate indices of refraction.
Knowledge:
Before performing the lab, all the lab member read through each experiment so that we could
familiarize ourselves with the various equipments. The first few experiments were a lot easier
as it was based solely on observations but as we progressed through, the experiments became
more challenging and time-consuming because of the measurements and calculations. This is
why the later experiments took a alot longer than the earlier ones and prevented us to
complete all seventeen experiments. But despite this, we were able to complete majority of the
experiments. If more time was available, our group could have completed all the experiments.