#  Astrophysical Principles - Radiation 

 



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### Inverse Square Law

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Large climbing frame shaped to show inverse square relation of light intensity (smaller version also available).

### Tower of Spectra

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Assembly of three gas discharge tubes and white light source for spectral analysis with diffraction gratings.  
\[[In-Depth Description](/presentations/tower-spectra)\]

### Sodium Absorption

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Burning of sodium bicarbonate in Bunsen flame produces sodium absorption lines in continuous spectrum.   
\[[In-Depth Description](/presentations/sodium-absorption)\]

### Boltzmann Distribution

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Mechanical analog of energy level populations which models a gas at essentially any temperature.

### Collisional Broadening

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Na D-doublet absorption lines broaden into one large absorption band due to increase in pressure/temperature.  
\[[In-Depth Description](/presentations/collisional-broadening)\]

### Spectrum Piano

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The visible part of the electromagnetic spectrum is represented by less than an octave of the keys; UV, IR, and microwaves are also indicated.  
\[[In-Depth Description](/presentations/spectrum-piano)\]

### Relativity Train

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Demonstration of time dilation and length contraction gedanken experiment using a train on a track.  
\[[In-Depth Description](/presentations/relativity-train)\]

### Bouncing Photon

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A photon (modeled by a bouncing ping-pong ball) is observed from two reference frames and provides the motivation for time dilation.  
\[[In-Depth Description](/presentations/bouncing-photon)\]

### Doppler Ball

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Plastic Wiffle Ball with built-in shriek to throw past (or at) your audience.  
\[[In-Depth Description](/presentations/doppler-ball)\]

### Doppler Turntable

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Two speakers, one at each end of rotating platform; beating due to frequency shift of speakers travelling in opposite directions.  
\[[In-Depth Description](/presentations/doppler-turntable)\]

### Doppler Whirler

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A high-pitched alarm on the end of a rope is whirled about the head.  
\[[In-Depth Description](/presentations/doppler-whirler)\]

### Doppler Tuning Forks

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Run towards the blackboard carrying a tuning fork...  
\[[In-Depth Description](/presentations/doppler-tuning-forks)\]

### Doppler Effect

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Listen to the doppler shift of light as a moving mirror reflects laser light onto a photodetector.

### Elastic Light

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Wave drawn on elastic sheet shows redshift due to expansion of space.  
\[[In-Depth Description](/presentations/elastic-light)\]

### Contact Us

**Mailing Address**: Lecture Demonstration Services, Science Center, Rm B-08A, 1 Oxford Street, Cambridge, MA 02138  
**Campus Location**: Science Center B-08A | **Tel**: (617) 495-5824 | **Email**: scidemos-at-fas.harvard.edu