NASA Hubble Heritage image of NGC 6751 a planetary nebulae 6500 LY away.

Magnifying a hydrogen atom 1012 times. The electron cloud is 4 Magnifying a hydrogen atom 1012 times. The electron cloud is 4.5 times the size of the atom. The nucleus, a single proton, is the size of a grape seed. Conclusion, atoms are really small. If a baseball were enlarged to the size of the earth then atoms would only be the side of grapes.

Permitted orbits of a few elements, if electrons had semi-classical orbits which they do not since they are actually probability distributions. This is a poor picture, actually likely to confuse more students than to enlighten. As an energy level picture this makes some current sense, but do not think of this as a picture in length space.

Permitted energy levels for an atom Permitted energy levels for an atom. This actually make a little more sense until you realize that the definiteness of the energy level is actually dependent upon the lifetime of the state.

First frame, energy does not match permitted level First frame, energy does not match permitted level. Second frame energy does match and is absorbed so the electron is meta-stable in the third frame. After a while the meta-stable state the electron returns to the lower energy state and releases a photon.

Continuous spectrums caused by solids, liquids, or high pressure gasses of different temperature.

Continuous spectrum

Absorption spectrum, star with bright photospheres produce continuous spectrums which their atmospheres absorbed some of the light.

Emission spectrum. The atmospheres of a small minority of stars does produce an emission spectrum.

Stars for instance have absorption spectra, in fact, the absorption line tell you what the temperature of the star is.

Gustav Robert Kirchhoff of Kirchhoff’s laws.

Energy level diagram of hydrogen with some of the spectral sequences names. Notice that the difference between the radius of the different energy levels is proportional to energy, but the round shape means nothing. Electrons really do not travel in circular or elliptical obits in space they are actually probability distributions.

An excited Balmer hydrogen cloud nebulae that appears red or pink because of the red, blue, and violet Balmer color. The red line is brightest in this low density cloud of hydrogen atoms in this typical nebulae. The word nebulae means cloud or ghost in ancient Greek.

Intensity plots versus wavelength at the bottom versus color brightness versus wavelength. Notice the absorption, dark line!

Line strengths for hydrogen versus temperature of the star.

Line strengths versus star temperature for hydrogen and now ionized calcium.

Line strengths for many absorption line versus star temperature.

A spectral sequence of stars spectral types A spectral sequence of stars spectral types. Actually these are computer simulated spectra. The violet end extends into the near ultraviolet so the H and K line of calcium is shown. Humans can only see to around 420 to 700 nm. We actually see best around 530 nm. Nm is nanometers, 10-9 meters.

Some more computer simulated stellar spectra in a sequence, (this time intensity is plotted) but this time the spectra extend even further into the ultraviolet and infrared than humans see.

L spectral type stars contrasted with M8 stars L spectral type stars contrasted with M8 stars. This picture extends a good way down into the infrared.

Doppler shift

Doppler shifts with sound.

Doppler shifts with light.