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(1) NAME OF SOURCE: Outdoor wall lighting. PHYSICAL DESCRIPTION: Large outdoor wall light with one large halogen bulb; yellowish-white when not...

Can you please check my description of some light sources I have observed? Please tell me if there are mistakes in my deductions.
(1) NAME OF SOURCE: Outdoor wall lighting. PHYSICAL DESCRIPTION: Large outdoor wall light with one large halogen bulb; yellowish-white when not viewed through grating; very bright (much brighter than fluorescent lamp described above); very warm to the touch. In comparison, the fluorescent tubes described above are rather cool. TYPE OF SPECTRUM: Continuous spectrum. ADDITIONAL COMMENTS: 1.Predominance of red and yellow light in the spectrum. Fairly little purple light. 2. Blue and purple light become more accentuated in spectrum when one moves the grating further away from the light source. PHYSICAL PROCESS: An electric current is sent through the tungsten filament to generate heat (hence the warmth of the bulb). In turn, the heat from the hot solid body (tungsten filament) emits light in a typical blackbody radiation. The distribution of colors within the spectra and wavelength of maximum intensity simply depend on the temperature of the object. The temperature of a typical tungsten halogen bulb is 3250°K. According to Wien's law, this bulb would generate light more intensely at 923 nm, which is in the infrared spectrum. This explains the warmth of the bulb. In the visible spectrum, the bulb radiates more energy between 600-700 nm. Little UV and visible purple light is present because the fused silica quartz envelope of the tungsten halogen bulb absorbs very little of the very short-wavelength light. (2) NAME OF SOURCE: Sun PHYSICAL DESCRIPTION: G2 star at about a distance of 1 AU from observation point (Earth). Is extremely bright and looks yellow-white in the sky. TYPE OF SPECTRUM: Sunlight is supposed to have an absorption spectrum, but I did not find absorption lines on the gratings. I saw only a seemingly continuous spectrum. The gratings could not have been strong enough to resolve the spectral lines. This issue in elaborated upon in the 'Discussion of Results' section. ADDITIONAL COMMENTS: 1. At a certain angle, the light forms a thin, straight, clear, extremely bright, and continuous spectrum on the grating. That line shows a clear progression of colors as well as a mixing of colors at their meeting points: red, orange, yellow, green, cyan, blue, purple, bright purple-pink, red, ect. No color (wavelength) had a striking dominance over the others. PHYSICAL PROCESS: Even if it was not seen during this observational exercise, the spectrum of sunlight is an absorption one. Here is how it is produced: The visible light produced in the incandescent gas in the deep dense layers of the Sun has a continuous spectrum. However, when that light passes through the less-dense chromosphere, chromospheric atoms absorb photons of appropriate wavelengths. This produces dark absorption lines (called Fraunhofer lines) of elements such as hydrogen and helium in the spectrum. Other photons are absorbed and other absorption lines are produced when the sunlight passes through Earth's atmosphere to reach my observation point (on Earth's surface).
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(3) NAME OF SOURCE: Fluorescent lamp PHYSICAL DESCRIPTION: Two medium-size fluorescent tubes in a lamp designed for camping trips. Fairly bright, but not as bright as an incandescent bulb. TYPE OF SPECTRUM: Continuous spectrum on which there are emission lines. ADDITIONAL COMMENTS: 1. The continuous spectrum was dominated by green light. There was comparatively little red. Yellow light was not present in the continuous spectrum and the little amount of blue and purple light were mixed together. 2. Three characteristic emission lines of mercury were seen. The first one is the violet line at 435 nm, the second one is the green one at 546 nm. Mercury is supposed to have a pair of yellow emission lines at 576 and 579 nm. The diffraction grating used is quite small and of fairly poor quality, which might have resulted in me seeing the two close yellow lines as one. PHYSICAL PROCESS: Fluorescent lamps generate visible light by exciting mercury vapor. The mercury vapor then emits UV light that causes phosphor to produce light through fluorescence. Fluorescence is the emission of excessive radiation (especially as visible light) after bombardment by UV light or electrons. The continuous spectrum is produced by phosphor lining the inside of the tubes, while the bright emission lines are created by the excited mercury. How does the excitation of the mercury produce light of specific wavelengths (435 nm, 576 nm, 579 nm)? The state of excitation of the electrons in the mercury does not last long. An excited electron subsequently returns to the ground state and releases a specific wavelength of light that is equal to the difference between its excited energy level and the ground state. (4) NAME OF SOURCE: Streetlamp PHYSICAL DESCRIPTION: High-pressure sodium (HPS) streetlamp with one large bulb in a city center; yellow when not viewed through the grating; very bright. TYPE OF SPECTRUM: Emission and absorption spectrum ADDITIONAL COMMENTS: 1. Some emission lines (at the red, orange, and purple wavelengths) are strangely very thick. PHYSICAL PROCESS: -In an HPS lamp, a small amount of sodium is heated until it is in vapor form. Electricity is then used to excite the vaporous sodium molecules into emitting light. The lamp also contains a small amount of mercury, which is used to get the lamp initially started. -The emission lines are created by both sodium and mercury, which are excited. The two yellow lines at 588-599 nm at the right of the spectrum are two characteristic emission lines of sodium: D 1 and D 2 . Those particular lines are created the same way emission lines of mercury are
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Dear Student Please find... View the full answer


Your deductions about light source are correct. It is only that you have some grammatical mistakes in
your writeup. Please correct them, everything else is fine
(1) NAME OF SOURCE: Outdoor wall...

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