geometrical optics
INVESTIGATION #1: Diverging and Parallel Rays of Light
MATERIALS
Miniature light bulb
Power Supply / Battery
Light bulb holder
Meter Stick
Laser Pointer
Face powder
Transparent Ruler
Small paper disk
Graphing paper
RESULTS
Based on the observation, the rays from the light bulb were spreading out from the light source. It produced light wave fronts that spread light near the source. The rays were straight lines drawn in the direction of the motion.
The laser beam couldn’t be seen very well without the face powder. The light from the laser appeared different from the light bulb. The light bulb spread light around it while the laser only spread light into one direction where it was pointed. Rays from the laser couldn’t pass through points which are not in the direction of its motion.
DISCUSSION
The rays from the light bulb are diverging because they are distributed and separated to different directions. The light from a point source is also composed of diverging spherical waves. On the other hand, the rays from the laser pointer are parallel since they only go through a straight or parallel direction and they hardly spread out at all.
CONCLUSION
Hence, rays from a point source are called diverging rays while rays from a laser are called parallel rays.
INVESTIGATION #2: Laws of Reflection and Refraction
MATERIALS
Laser pointer
Glass rod
Semicircular clear chamber filled with water
Face powder
Pencil
Ruler
Protractor
Graphing paper
RESULTS
MATERIALS
Laser pointer
Glass rod
Semicircular clear chamber filled with water
Face powder
Pencil
Ruler
Protractor
Graphing paper
RESULTS
DISCUSSION
As observed from the experiment, the angle of incidence was equal to the angle of reflection for the three cases. The reflected ray was also in the same plane where the incident ray was.
Compared to the angle of incidence, the angle of refraction was smaller. This was due to the optical densities of two media. Since water is more optically dense, the refracted ray was bent toward the normal making the smaller angle. Refraction occurs when the direction of light is changed when it passes through two materials of different optical densities like the one happened in the experiment. This relationship of the angles of incidence and refraction is stated in the Snell’s Law of Refraction.
CONCLUSION
Therefore, the law of reflection states that the angle of incidence is equal to the angle of reflection and these angles and the normal lie on the same plane. The Snell’s law of refraction states that n1sin θ1 is equal to n2sin θ2. The “n” refers to the index of refraction that describes the optical density of the material.
SOURCES: Level Science Physics Learning Through Diagrams i-Physics
INVESTIGATION #3: Dispersion and the Rainbow
MATERIALS
Laser pointer
Flash light with a narrow slit
Prism Solid
clear cylinder
DIAGRAM
As observed from the experiment, the angle of incidence was equal to the angle of reflection for the three cases. The reflected ray was also in the same plane where the incident ray was.
Compared to the angle of incidence, the angle of refraction was smaller. This was due to the optical densities of two media. Since water is more optically dense, the refracted ray was bent toward the normal making the smaller angle. Refraction occurs when the direction of light is changed when it passes through two materials of different optical densities like the one happened in the experiment. This relationship of the angles of incidence and refraction is stated in the Snell’s Law of Refraction.
CONCLUSION
Therefore, the law of reflection states that the angle of incidence is equal to the angle of reflection and these angles and the normal lie on the same plane. The Snell’s law of refraction states that n1sin θ1 is equal to n2sin θ2. The “n” refers to the index of refraction that describes the optical density of the material.
SOURCES: Level Science Physics Learning Through Diagrams i-Physics
INVESTIGATION #3: Dispersion and the Rainbow
MATERIALS
Laser pointer
Flash light with a narrow slit
Prism Solid
clear cylinder
DIAGRAM
RESULTS
When the light of the flash light came out from the right side of the prism, a rainbow of colors could be seen. Instead of the white light, it had been dispersed into red, orange, yellow, green, blue, indigo, and violet. The color which was refracted the most was violet and the color which was refracted the least was red. Based on the observation, the index of refraction of violet is larger than the red light.
When the laser light came out from the right side of the prism, no rainbow of colors could be seen. Since the laser pointer has only red light incident on the prism, then red light will be refracted as well.
DISCUSSION
Dispersion is the spreading of white light into its full spectrum of wavelengths. Refraction is responsible for dispersion in rainbows. We know that the index of refraction n, depends on the medium. But for a given medium, n also depends on wavelength. The index of refraction increases as wavelength decreases. Thus, violet light is bent more than red light as shown for a prism.
CONCLUSION
Refraction occurs in the dispersion of white light into spectrum of colors. This will produce rainbows. The index of refraction of the transmitted rays of colors is inversely proportional to its wavelength. As the wavelength decreases, the index of refraction increases thus it is more bent toward the normal.
SOURCES i-Physics IV OpenStax CNX (http://cnx.org/contents/c221d1fc-6368-440d-9d75-00f45fc0570d@5)
When the light of the flash light came out from the right side of the prism, a rainbow of colors could be seen. Instead of the white light, it had been dispersed into red, orange, yellow, green, blue, indigo, and violet. The color which was refracted the most was violet and the color which was refracted the least was red. Based on the observation, the index of refraction of violet is larger than the red light.
When the laser light came out from the right side of the prism, no rainbow of colors could be seen. Since the laser pointer has only red light incident on the prism, then red light will be refracted as well.
DISCUSSION
Dispersion is the spreading of white light into its full spectrum of wavelengths. Refraction is responsible for dispersion in rainbows. We know that the index of refraction n, depends on the medium. But for a given medium, n also depends on wavelength. The index of refraction increases as wavelength decreases. Thus, violet light is bent more than red light as shown for a prism.
CONCLUSION
Refraction occurs in the dispersion of white light into spectrum of colors. This will produce rainbows. The index of refraction of the transmitted rays of colors is inversely proportional to its wavelength. As the wavelength decreases, the index of refraction increases thus it is more bent toward the normal.
SOURCES i-Physics IV OpenStax CNX (http://cnx.org/contents/c221d1fc-6368-440d-9d75-00f45fc0570d@5)