Comparing Emission Spectra of Different Light Sources using SpectroVis Plus Mendiola, Wendy Kate C. School of Science and Engineering, Ateneo de Manila University Quezon City, Philippines 1800 wendy.mendiola@obf.ateneo.edu Abstract This paper discusses the emission spectra of different light sources and their impact on the human eyes. Artificial lights are important in determining the performance of the conversion of electricity into light. Different light sources provides a different spectra and this is important in architectural lighting in homes and in the industry. Using Logger Pro and Vernier SpectroVis Plus, analysis of LED, Compact Fluorescent Lamp, and Incandescent Fluorescent Lamp were performed. Based on the results, LED’s are the best artificial light source because they have energy saving properties and their spectrum is close to the spectrum of natural light. Keywords: light source, natural light, artificial light, emission spectra 1. Introduction Any object that has a temperature above absolute zero will radiate electromagnetic waves due to a process called thermal radiation. The human body radiates predominantly in the far infrared region. As temperature increases to around 798 K, thermal emission will start to enter the visible region and appear to the human eye as a red glow in a process called incandescence. Increasing the temperature further causes the color of light emitted to shift to smaller wavelengths. Thermal radiation is the process responsible for the light emitted by the sun and the incandescence of light bulbs. The sun has a surface temperature of about 5,778 K. It comprised of a number of wavelengths of visible light as well as other types of EM radiation that we cannot see. Sunlight in space is most intense between 470510 nanometers, which consists of blue and green colors. Everyday, we are bombarded by enormous spectrum of EM radiation and yet we are only able to see a portion of it called the visible light. When outdoors, majority of the light visible to humans is emitted from the sun. Indoors, we are exposed to visible light coming from artificial sources like fluorescent and incandescent light bulbs. Light sources for homes, cities, and industries are essential for our daily life. It uses more than 20% of the worldwide electricity production. It is just necessary to find ways for improving energy performance of the lighting products. This study focuses on comparing emission spectra of different light sources using Logger Pro and Vernier SpectroVis Plus. Ho: LED’s are the best artificial light source as they have energy saving properties and their spectrum is closer to that of natural light. 2. Methodology The spectrum of each light bulb is measured using the SpectroVis Plus. A single trial was done in measuring the spectrum of the three light sources. The results were analyzed using Logger Pro. The light sensor generates an intensity-wavelength graph that can be viewed Logger Pro. By analyzing the statistics, the minimum and maximum values for intensity were generated and a specific color is given depending on the portion of the spectrum that was analyzed. 3. Results and Discussion Table 1 LED Color Wavelength of the peaks (nm) Violet Green Green 446.9 523.4 568.2 1 Table 2 Incandescent Fluorescent Lamp Color Wavelength of the peaks (nm) Yellow Red Red 571.5 637.7 690.3 Table 3 Compact Fluorescent Lamp Color Wavelength of the peaks (nm) Green Green Yellow 520.9 541.6 576.5 An incandescent light bulb contains a tungsten filament that is heated when a current passes through it. At 2,000K, the filament starts to emit visible light. To prevent the wire from burning, the bulb is filled with gas, usually argon. The heat generated in the filament is transported to the surroundings through radiation, convection, and conduction. This type of bulb emits a greater proportion of red light than natural daylight. Emission even extends into the infrared part of the electromagnetic spectrum, which wastes energy and reduces the overall efficiency of the bulb. Figure 1 The emission spectrum in the visible range of a typical incandescent bulb A fluorescent lamp typically consists of a long, glass tube containing a low-pressure mixture of mercury and a rare gas, such as argon. Inside of this tube is a non-equilibrium discharge. This means that the electron temperature is different from the temperature of the gas mixture. Since the plasma is not in equilibrium, the electron impact reactions modify the chemical composition of the gas mixture in a manner governed by the collisional processes. These collisions can produce electronically excited neutrals, which can subsequently produce spontaneous emission of photons at specific wavelengths. Fluorescent lights often cause problems for people suffering from a visual disorder called Irlen syndrome, and people often complain of headaches and migraines when exposed to fluorescent lights for extended periods of time. The quantization is either due to direct emission from the plasma or by the phosphors, but to a human 2 eye, the light emitted still seems white. Like incandescent bulbs, fluorescent bulbs can be inefficient because the plasma needs to be sustained and it emits radiation in the non-visible range. Figure 2 The emission spectrum of a typical fluorescent bulb LED’s are the game changers of lighting industry as they are often more efficient in terms of luminous efficacy and durability. A typical consumer LED light bulbs operate at 10-20% of the power needed to run an incandescent bulb of comparable brightness. They also have lifetimes of over 25,000 hours, compared to only 1000 hours for incandescent bulbs. LEDs are more efficient than incandescent bulbs because they function in a very different way. Unlike incandescent bulbs, LEDs emit light over a very narrow range of wavelengths. Initially, red, green, and yellow LEDs were developed in the 1950s and 1960s. However, it was the invention of the blue LED that led to the creation of new, efficient white light sources. Blue light emitted from such LEDs can be used to stimulate a wider spectrum of emission from a phosphor layer around the LED casing, or can be directly combined with red and green LEDs to create white light. As shown in Figure 3, the LED spectra for a yellow phosphor setting gets closer to that of natural daylight. There is more blue light than the incandescent bulb and nearly all of the power is emitted within the visible spectrum. Figure 3 The emission spectrum of a typical LED bulb on a warm, white setting 3 Figure 4. Emission Spectra from daylight and typical incandescent, fluorescent, and LED bulbs The different emission spectra are plotted on the same axis on Figure 4. We can infer from the figure that LED’s provide the best lighting options among the three artificial lights tested. These three primary lighting sources all have different properties and spectral characteristics, but their maximum intensities all fall within the visible light range. The human brain adjusts automatically to the different light sources, and we interpret the colors of most objects around us as hardly changing when they are viewed under differing conditions of illumination. IV. Conclusion The experiment tested different spectra of artificial lights. The evolution adapted our eyes to the sunlight. So using light different from the spectrum of natural light can cause dry eyes. If left untreated, it can lead to more serious conditions. While none of the bulbs exactly reproduce natural daylight, the LED bulb is clearly the best approximation. All of the emission occurs within the visible range, making the device very efficient. References 1. 2. 3. 4. Fawzia Abdel-Rahman, Bethel Okeremgbo, Fatimah Alhamadah, Sakha Jamadar, Kevin Anthony & Mahmoud A. Saleh (2017) Caenorhabditis elegans as a model to study the impact of exposure to light emitting diode (LED) domestic lighting, Journal of Environmental Science and Health, Part A, 52:5, 433439, DOI: 10.1080/10934529.2016.1270676. Davidson, Michael W.,“Sources of Visible Light,” Retrieved June 23, 2022, from https://micro.magnet.fsu.edu/primer/lightandcolor/lightsourcesintro.html Smith, Daniel.” Calculating the Emission Spectra from Common Light Sources,” Retrieved June 23, 2022, from https://www.comsol.com/blogs/calculating-the-emission-spectra-from-common-light-sources/ Majka, Marcin, “Analysis of the effect of different light sources on the health of the eyes”, Retrieved June 23, 2022 from https://sciforum.net/manuscripts/933/manuscript.pdf. Acknowledgements Successful accomplishment of the experiment most especially the data collection in this paper would not be possible without the efforts of the following members of this group: Verniese Chen, Wendy Mendiola, Lance Harvey Saavedra and Geneena Villarico. 4 Appendix Table 1 LED Color Wavelength of the peaks (nm) Violet Green Green 446.9 523.4 568.2 Table 2 Incandescent Fluorescent Lamp Color Wavelength of the peaks (nm) Yellow Red Red 571.5 637.7 690.3 Table 3 Compact Fluorescent Lamp Color Wavelength of the peaks (nm) Green Green Yellow 520.9 541.6 576.5 5
