# Application of advanced spectrometer in geometrical optics?

Tags:
1. Jan 10, 2015

### Dorea

We have an advanced spectrometer in our geometrical optics lab! I'm seeking for any experiment in geometrical optics to include it!

2. Jan 11, 2015

### Quantum Defect

This spectrometer is useful for looking at atomic and molecular spectra. A very nice experiment would be to examine the spectrum of a propane or butane flame. The blue color of the flame is primarily due to emission from electronically excited C2. The major structure in the spectrum is due to the quantization of vibration in the excited and ground electronic states. c.f. http://en.wikipedia.org/wiki/Swan_band

You can also measure the spectra of discharge lamps. It is interesting to look at the difference between hydrogen and deuterium lamps -- assuming that you can get access to a discharge lamp power supply with H and D lamps. Google "spectrum tube power supply" and "spectrum tube" to see where to buy these/what these look like. The power supply is ca. $100, the tubes are ca.$20/ea.

3. Jan 11, 2015

### Dorea

There's many application for it in wave optics. More, I'm asking for experiment in geometrical optics field for freshmen!

4. Jan 12, 2015

### Quantum Defect

I see. The only thing that I can think of is to do some work measuring refractive indices of materials (Snell's Law). With a small set of laser pointers, you could measure the change in refractive index as a function of wavelength (dispersion curves) for some simple solid materials. If you have a "water prism" you could also measure this for some pure liquids.

5. Jan 12, 2015

### Andy Resnick

Strictly speaking, I don't see how this is possible- geometrical optics is wavelength independent, and chromatic aberrations are likely beyond what you are thinking.

I suppose you could do some version of Snell's law, Fresnel reflection/transmission coefficients, etc if you have a monochromatic light source. Maybe something with double refraction (uniaxial crystal optics). But all of these are ad-hoc excuses for using the instrument, as opposed to actually learning something.

Why did you guys decide to use this for a geometrical optics lab, as opposed to a wave optics lab?

6. Jan 12, 2015

### Staff: Mentor

Instead of using Snell's Law directly, try using the minimum deviation angle of a prism. While watching a spectrum line through the viewing telescope, rotate the prism. You should be able to see the line move back and forth across your field of view, and locate the extreme angle in one direction.