White Light Lab
Introduction: To do the lab exercises for this lesson, you need to know a little bit about light. White light consists of all the colors of the rainbow mixed together. Diffraction refers to various phenomena which occur when a wave encounters an obstacle. In classical physics, the diffraction phenomenon is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Isaac Newton thought that light must be a particle because particles of light that travels in straight lines until they are stopped by some object that blocks its path. When it is passed through a prism or a diffraction grating, the colors are separated into what we call a spectrum. A diffraction grating is a piece of glass
…show more content…
or clear plastic into which have been etched a series of extremely narrow lines. If you were to look at a grating, the lines would be too small to see, but you would see a rainbow effect of the surface. For example, the lines on the surface of a CD are narrow enough to diffract visible light, so that when you look at the light reflected off of the surface, you observe a rainbow effect. For this experiment, I will be using a diffraction grating to look at six different objects. These objects include an incandescent bulb, a light up candle, a fluorescent light, a neon light, LED light and a bug light.
Incandescent light/bulb: A light bulb consists of the glass bulb enclosing a tungsten wire filament that makes electrical connection with the universal metal base that screws into an electrical outlet. The bulb is at reduced atmospheric pressure (about 80% of atmospheric) usually containing an inert gas such as nitrogen. As I placed the diffraction grating over my eye, I was able to see a rainbow spectrum like the one I saw with the candle expect that this one was not wavy, it was still. The light bulb rainbow spectrum was more vertical than the candle. The three main colors of the spectrum were blue, green and red. There was a mixture of yellow and orange in the spectrum. An incandescent light has a continuous spectrum with all visible colors present. There are no bright lines and no dark lines in the spectrum. This is one of the most important spectra, a blackbody spectrum emitted by a hot object.
Candle Flame: The candle flame was a little bit different. For this experiment, you have to make sure the candle has a steady flame. The you have to take the plate and place it on the flame. This results in a black/burning color on the plate. Then, you have to carefully blow on the flame. Finally, you have to hold a knife tip covered in salt in the flame. While doing this, I saw two rainbow spectrums - one on the left and one on the right side of the candle. The rainbow spectrum was short and wavy. The spectrum of the candle flame is continuous; there are no visible discrete lines.
Fluorescent light: The spectrum of a fluorescent light has bright lines and a discrete spectrum.
The bright lines come from mercury gas inside the tube while the continuous spectrum comes from the phosphor coating lining the interior of the tube. After doing a little bit of research on the internet, I discovered that fluorescent light bulbs contain a mixture of inert gases (usually argon and neon) together with a drop of mercury at low pressure, so that some of the mercury atoms form a gas in the tube. I also learned that the inside of the glass tube is coated with a phosphor coating that is designed to absorb the UV light (radioactive absorption). For this experiment, a straight tube was used. As I placard the direction grating over my eye, I was able to thinner vertical lines. At this time, I was able to notice how the rainbow spectrum was different of that of the light bulb and candle. The rainbow spectrum was different than the previous two because I was now able to see a forth color, orange. The color blue was still thicker than the other colors. The four colors were blue, green, orange and red.
Neon light: For this experiment, I used a friends open sign neon light. During lecture, I learned that even though they are called neon lights, the lights do not necessarily contain neon gas, some contain argon or other gasses to produce different colors. The red ones contain neon. I conducted this experiment the same way I did the previous three. Placing a diffraction grating over my eye, I was able to see a straight rainbow spectrum. The spectrum of the neon light had several bright lines. The red lines were brightest. The four main colors were green, orange and red. This spectrum showed a discrete
spectrum. Light emitting diodes, LEDs; For the next experiment, I choose to use a diffraction grating on a LED light. These come in many colors from red, orange, yellow and green to blue.
In Light emitting diodes electrons in a higher energy conduction band drop into holes in a lower energy band. The energy lost by the electrons is emitted as light. Therefore, there is usually one brightest color of light that appears as a line in the spectrum of the LED. In addition to the bright line there is usually also a dimmer, continuous emission of lower energy light. This lower energy light is produced when electrons decay to or from impurity states between the main energy bands. When I placed a diffraction grating over my eye, it showed a continuous spectrum.
Bug light: For my final experiment, I thought it would be interesting to see the diffraction grating on a bug light. Bug lights are typically red or yellow in color. The particular one I used was red. As I placed my diffracting ratting over my eye, I was able to see rainbow spectrums containing the color green, red, orange, and yellow. The spectrum was continuous. I was surprised that the color blue/violet was not one of the colors in the spectrum. I found this odd and for a moment thought that there was something wrong with my diffraction grating. After doing this experiment over and over, I kept getting the same results. I decided to go online and try to find a solution. To my surprise, I was able to find the answer. One particle article described how most insects are attracted to blue and violet visible light, as well as UV radiation. In addition, insect’s eye structure is different than humans and allows them to perceive UV radiation as visible light. Insects are only attracted to lights that they can see, so any light that minimizes production of those wavelengths will not attract bugs.
As a result, l learned that the spectrum color each had a different wavelength. Red, with the longest wavelength, is diffracted most; and violet, with the shortest wavelength, is diffracted least. Because each color is diffracted a different amount, each color bends at a different angle. The result is a separation of white light into the seven major colors of the spectrum or rainbow. The diffraction grating consists of many narrow slits provided for the diffraction of the light. Aside for this, one important fact that I learned while doing this experiment and researching diffraction grating, was who discovered the word diffraction. The individual was an Italian scientist named Francesco Maria Grimaldi, who coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665.
or clear plastic into which have been etched a series of extremely narrow lines. If you were to look at a grating, the lines would be too small to see, but you would see a rainbow effect of the surface. For example, the lines on the surface of a CD are narrow enough to diffract visible light, so that when you look at the light reflected off of the surface, you observe a rainbow effect. For this experiment, I will be using a diffraction grating to look at six different objects. These objects include an incandescent bulb, a light up candle, a fluorescent light, a neon light, LED light and a bug light.
Incandescent light/bulb: A light bulb consists of the glass bulb enclosing a tungsten wire filament that makes electrical connection with the universal metal base that screws into an electrical outlet. The bulb is at reduced atmospheric pressure (about 80% of atmospheric) usually containing an inert gas such as nitrogen. As I placed the diffraction grating over my eye, I was able to see a rainbow spectrum like the one I saw with the candle expect that this one was not wavy, it was still. The light bulb rainbow spectrum was more vertical than the candle. The three main colors of the spectrum were blue, green and red. There was a mixture of yellow and orange in the spectrum. An incandescent light has a continuous spectrum with all visible colors present. There are no bright lines and no dark lines in the spectrum. This is one of the most important spectra, a blackbody spectrum emitted by a hot object.
Candle Flame: The candle flame was a little bit different. For this experiment, you have to make sure the candle has a steady flame. The you have to take the plate and place it on the flame. This results in a black/burning color on the plate. Then, you have to carefully blow on the flame. Finally, you have to hold a knife tip covered in salt in the flame. While doing this, I saw two rainbow spectrums - one on the left and one on the right side of the candle. The rainbow spectrum was short and wavy. The spectrum of the candle flame is continuous; there are no visible discrete lines.
Fluorescent light: The spectrum of a fluorescent light has bright lines and a discrete spectrum.
The bright lines come from mercury gas inside the tube while the continuous spectrum comes from the phosphor coating lining the interior of the tube. After doing a little bit of research on the internet, I discovered that fluorescent light bulbs contain a mixture of inert gases (usually argon and neon) together with a drop of mercury at low pressure, so that some of the mercury atoms form a gas in the tube. I also learned that the inside of the glass tube is coated with a phosphor coating that is designed to absorb the UV light (radioactive absorption). For this experiment, a straight tube was used. As I placard the direction grating over my eye, I was able to thinner vertical lines. At this time, I was able to notice how the rainbow spectrum was different of that of the light bulb and candle. The rainbow spectrum was different than the previous two because I was now able to see a forth color, orange. The color blue was still thicker than the other colors. The four colors were blue, green, orange and red.
Neon light: For this experiment, I used a friends open sign neon light. During lecture, I learned that even though they are called neon lights, the lights do not necessarily contain neon gas, some contain argon or other gasses to produce different colors. The red ones contain neon. I conducted this experiment the same way I did the previous three. Placing a diffraction grating over my eye, I was able to see a straight rainbow spectrum. The spectrum of the neon light had several bright lines. The red lines were brightest. The four main colors were green, orange and red. This spectrum showed a discrete
spectrum. Light emitting diodes, LEDs; For the next experiment, I choose to use a diffraction grating on a LED light. These come in many colors from red, orange, yellow and green to blue.
In Light emitting diodes electrons in a higher energy conduction band drop into holes in a lower energy band. The energy lost by the electrons is emitted as light. Therefore, there is usually one brightest color of light that appears as a line in the spectrum of the LED. In addition to the bright line there is usually also a dimmer, continuous emission of lower energy light. This lower energy light is produced when electrons decay to or from impurity states between the main energy bands. When I placed a diffraction grating over my eye, it showed a continuous spectrum.
Bug light: For my final experiment, I thought it would be interesting to see the diffraction grating on a bug light. Bug lights are typically red or yellow in color. The particular one I used was red. As I placed my diffracting ratting over my eye, I was able to see rainbow spectrums containing the color green, red, orange, and yellow. The spectrum was continuous. I was surprised that the color blue/violet was not one of the colors in the spectrum. I found this odd and for a moment thought that there was something wrong with my diffraction grating. After doing this experiment over and over, I kept getting the same results. I decided to go online and try to find a solution. To my surprise, I was able to find the answer. One particle article described how most insects are attracted to blue and violet visible light, as well as UV radiation. In addition, insect’s eye structure is different than humans and allows them to perceive UV radiation as visible light. Insects are only attracted to lights that they can see, so any light that minimizes production of those wavelengths will not attract bugs.
As a result, l learned that the spectrum color each had a different wavelength. Red, with the longest wavelength, is diffracted most; and violet, with the shortest wavelength, is diffracted least. Because each color is diffracted a different amount, each color bends at a different angle. The result is a separation of white light into the seven major colors of the spectrum or rainbow. The diffraction grating consists of many narrow slits provided for the diffraction of the light. Aside for this, one important fact that I learned while doing this experiment and researching diffraction grating, was who discovered the word diffraction. The individual was an Italian scientist named Francesco Maria Grimaldi, who coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665.