Wk5: Dispersion, Line Spectra, and Filters Abbreviations:
b/w = between
Friday, October 30, 2020 10:37 PM w/ = with
INC = increase
DEC = decrease
Ex. = example
• Behavior of a laser beam depends on it's light wavelength (l).
Lab Report Notes
Lab's Objectives: prism is used to show that the index of refraction (n) depends on the wavelength,
• (5.3.2) Observe the colors radiated by an incandescent lamp.
filters are used to show that some materials (filters) transmit radiation at one wavelength but absorb
it at another, and studying gas lamps reveal that different sources emit radiation at different
wavelengths.
• Speed of a traveling wave: v = l/T = fl
○ T: time interval b/w crests at a fixed position.
• Straight through angle: 179.5 + 25arcmin(or 0.4167degrees) = 179.917 -> 179.92degrees
○ f: frequency / # of crests that pass a fixed point per second. Reciprocal of T.
25arcmin/60 = 0.4167degrees
• Speed of light in a vacuum: v = c = 3.00E8 m/s.
• Sequence of colors: The colors radiated by the desk lamp through the spectrometer are red,
○ c is constant -> Light waves w/ different wavelengths have different frequencies too.
yellow, green, blue and violet. All the colors in the rainbow can be seen; this implies that
• Photon: light when it is acting like a particle. Carries energy (E) that depends on its
the prism in the spectrometer is transmitting light from a continuous spectrum of
wavelength and freq. E = hf = hc/l
wavelengths (all colors are bouncing off the object and reflecting into our eyeballs).
○ Planck's constant: h = 6.63E-34 Js (Joules second).
• Narrowest band: The narrowest band in the color spectrum appears to be the orange (region
○ Photons of red visible light carry less energy that of UV light b/c red photons have much
between red and yellow) color strip.
longer wavelengths.
• (5.3.3) Measure the index of refraction of the prism.
• lmax: wavelength where maximum photons are emitted; depends solely on object's
temperature. λmax α T^-1, where temp is measured in degrees Kelvin.
• Even though all objects who emit temperature continually radiate photons, most likely in a
spectrum of wavelengths, some materials can emit light at a very specific set of wavelengths. -
>
• Dmin: Avg angle - straight thru angle
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