Lab 7: Spectra

Tiara Cui

WED Lab

22 February 2017

Lab 7: Introduction to Spectroscopy

1. Assumptions

1. This result of the gas tubes exhibiting radiation verifies our current description of the orbital structure of the atom as any charged particle moving on a path emits electromagnetic radiation. Therefore, by having the Bohr model and the orbital structure that represents a fixed size and energy (energy of electron depends on the orbit’s size/allowed energy levels), radiation occurs only when the electron jumps from one orbit to another by absorbing or emitting a photon with the right wavelength.

1. Consequences

1. Sun: Continuous Spectra → comes from hot, opaque source (solid/dense gas) and must use light that has all wavelengths of visible light (sun is elf-luminous)

Planets: Partial absorption and partial reflection means that part of the spectrum will be taken away, thus absorption lines come from partial absorption

Earth’s Moon: Absorption lines → moon reflects the light from the sun therefore will have light, however because the moon hardly gives off any light by itself, there are gaps within the spectrum indicating there is no light being emitted.

1. Because its only electron is “missing,” and photons/light are created and destroyed by electrons jumping from one orbit to another, ionized hydrogen would be unable to emit or absorb light, therefore not having a spectrum.
2. If we were to take a cloud of initially cold hydrogen gas, and slowly increase its temperature, the brightness of the spectral emission lines will change; one way to generate light is to heat something up, thus this result could be used to determine the temperature of the hydrogen gas (reddish = cooler & bluish/whitish = hotter)
3. Yes, you would expect to find (given the right kind of camera) spectral lines outside of the visible region of the spectrum because if an object is moving towards us its entire spectrum will shift to shorter wavelengths, while if an object were to move away from us the spectrum is shifted into longer wavelengths (Doppler Effect), preventing us from seeing those spectral lines. Furthermore, in terms of Balmer’s formula, as n gets larger, the wavelength gets closer to a value moving towards the visible region of the spectrum (Balmer series).

1. Conclusions

1. Emission Lines: hydrogen, helium, neon, argon, krypton, mercury, xenon fluorescent bulb

Continuous Spectra: sun (some absorption lines), tungsten bulb