True or False: The Lyman series lines of hydrogen all lie in teh infrared?

Answer 1

False. The Lyman-alpha line of hydrogen is in the far ultraviolet part of the electromagnetic spectrum.

Answer 2

FALSE!

Lyman alpha lies at 1216 Å; the "Lyman limit" (where all the Lyman lines crowd together) is at 912 Å . This range of the Lyman series (912 to 1216 Å) lies FAR in the ultra-violet part of the spectrum.

The atmosphere effectively prevents radiation of wavelengths shorter than about 3600 Å reaching the Earth's surface from space. So it wasn't until balloons, rockets or finally satellites were sent high enough that we could learn much about this ultraviolet part of the radiation flooding through the Universe.

However, an interesting thing happened once large enough redshifts of quasars etc. were observed. For objects of redshift
' z ,' the observed wavelengths are longer than the origional, emitted redshifts by a factor of (1 + z).

So, once z was ≥ 2, (1 + z) became ≥ 3, meaning that the observed wavelength of Lyman alpha became not just 1216 Å, but rather ≥ 3648 Å. FINALLY, then, that RED-SHIFTED Lyman alpha could reach Earth's surface!

Since that time, redshifts of 3, 4, 5, 6, ... have been discovered, with the consequence that the problem is now finally occurring at the OTHER end of the visible spectrum: Lyman alpha in those objects observed with the highest red shifts have finally been shifted ALL the way FROM the ultra-violet, THROUGH the visible spectrum and now beyond that INTO the far infra-red. But that is NOT where they naturally lie, in their own rest-frame.

Live long and prosper.

POSTSCRIPT : 'Ras J' (immediately above) is COMPLETELY WRONG, and his was about as BLATANT and INDISCRIMINATE a case of misreferencing as I have ever seen. The link he gives, to justify his answer of "True," is to a homework or test question sheet which simply asserts that "The Lyman series lines of hydrogen all lie in the infra-red" AS A TRUE/FALSE QUESTION. (YES, it's the VERY same, completely unresolved question.) That DOESN't mean you can take such a bald statement as scientific fact !!

Answer 3

Would you WANT to see much ultraviolet getting through our atmosphere? It's called the ozone layer - be glad it's there.

Answer 4

True