Theory: How does a laser work Atoms and molecules consist of electrons and nucle
ID: 1620023 • Letter: T
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Theory: How does a laser work Atoms and molecules consist of electrons and nuclei. When no bonds exist between atoms, electrons are on discrete energy levels called orbitals: those levels where electrons reside at zero degree Kelvin are called ground states, and those above them are called excited states. Hydrogen spectrum (Balmer experiment) reveals the energy levels in hydrogen atoms, and the results from the dye absorption experiment indicate that large molecules also have energy levels, though they may not be discrete anymore. Question #1 Why does the Balmer series have sharp lines, and dyes have a broad absorption peaks? The total number of electrons on a specific level or orbital is defined as the population of that level. Under normal conditions, the population at a higher (electronic) energy level is smaller than that at a lower one. More precisely, the population is known to follow the Boltzmann distribution. Therefore, there is no lasing under normal conditions unless a population inversion is achieved, meaning a higher level actually has more electrons on it. Lasing occurs due to interactions of photons with population invented medium. The medium can absorb photons and cause electrons to jump from lower states to higher states. It can also emit spontaneous emission in which photons are released when electrons jump from an upper state to a lower state without any external disturbance. More importantly, it can also emit stimulated radiation. In this case, one or more photons are emitted when electronic transitions from an upper level to a lower level are triggered by another photon Laser works because of the existence of population inversion and stimulated emission. In a well-constructed cavity, photons from spontaneous emission are reflected off the two mirrors sandwiching the laser medium. When these photons pass through the medium again, they can induce a large amount of stimulated radiation, which can be subsequently amplified again after passing through the medium Lasers share the following characteristics not available from conventional light sources 1. Monochromaticity: Most lasers emit light with a very narrow spectral width 2. Directionality: Laser beams diverge very slowly or can be corrected with lenses without losing much of their power. 3. Coherence: All the photons resemble each other by their physical properties.Explanation / Answer
in the balmer series(hydrogen atom) every electron has a discrete energy levels which on irradiated gives a specific energy level.In other words you can say that every transaction of electron has specific frequency.and when these fall on screen they give very sharp image on sensor screen
but with the dye it has different electrons with nearby energy levels, so when irradiated gives a broad peaks.
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