this is one of our funnest demonstrations to show atomic spectra i'm going to show the spectrum of a uh an an incandescent bulb which is continuous and then I'm going to show the spectra of four different elements mercury nitrogen neon and especially hydrogen hydrogen will be important in the labs and in many other applications so to show a spectrum what we use is is called a defraction grading this looks like a piece of clear plastic but it's not it is uh actually a piece of clear plastic on which an image has been inscribed with dark line clear line dark line clear line with about 10 to 13,000 lines per inch so it's called a grading um just like a street grate it has lines through it and this allows you to resolve the spectrum of um of a source of light in the same way that a prism will resolve a spectrum so what we're going to do is to place this uh defraction grading in front of a camera and show you the view of this continuous um source with the defraction grading in place and what you'll see uh in the image is is the the image of the of the incandescent bulb itself and then to the right and to the left you'll see uh a rainbow spectrum that shows which what wavelengths are present in this you'll see um as you look on the right side uh violet through all the colors of the spectrum all the way through red so that's a continuous spectrum we'll try next to um to create to look at a a discrete spectrum of mercury now what this is is a it's a discharge tube it has mercury in it and what I'll do is um energize this tube uh uh apply a voltage to the tube and that causes the the gas in it to emit spectral lines according to the spectrum of the of the element that we're using in this case mercury so I'm going to locate this it's proper spot turn off the continuous spectrum so this is a mercury spectrum uh without the defraction grading and let me get it in focus here it's a bluish colored uh spectrum there are um mercury vapor lights that are used as um street lights so this may look similar to you this bluish tint to the mercury vapor now let's try it with the diffraction grading in place and what you see in this case are uh a green line and a blue line predominantly in this mercury spectrum uh next we will try a nitrogen spectrum i'm using this fur to prevent burning flesh so this is nitrogen spectrum and with the defraction grading in place we see a number of lines present some red orange yellow green and a a violet uh turquoiseish colored line that's nitrogen two more this is neon there's a beautiful orange look to it and when the defraction grading is in place you see a large number of red and orange lines this is exactly um what's used for neon lights the original neon light was made out of neon like this there there are other gases that are used to to to form um signs but but neon was really where it uh where it started off has a beautiful bright uh reddish orange spectrum so So this is hydrogen it has a a reddish cast to it and uh when the defraction grading is is in place you'll see three lines uh the farthest from the central image is a a red line that's the hydrogen alpha line and it is um very important in star images uh a lot of uh nebula in the in the sky have hydrogen alpha line as one of their prominent um spectral lines then there's a turquoise colored line greenish blue is the hydrogen beta line uh both from the Balmer series and we'll talk about those or have talked about those in class and then finally the hydrogen gamma line is a um violet line is generally considered to be the the one that's th those three lines are visible in the the hydrogen spectrum those lines are associated with transitions of the electron in the hydrogen atom from a higher state to a lower state in this case the second energy level is the final state and then higher uh energy levels it starts from higher level and goes down to the second energy level to get the bomber spectrum that is um continuous and emission spectrum