Summer 2010 Questions and Resources

Consider the transition from the 2P orbital to the 1s orbital in Hydrogen.

There are two wavefunctions here, psi1 and psi2. These wave functions are stationary in time.

However during the transition we get the sum of two wave functions and the sum varies in time, creating an oscillating charge which is a dipole electric radiator.

Here is an illustration to show this.

Sum of 1S and 2P orbitals

The probability of finding an electron is proportional to psi squared.


Great physics apps in particular ripple tank apps are available by searching for falstad


Here are the notes from anAudacity Handout


Don Rathjen activities

Paper Tape Timer reference, mathematics:

Fan Cart


The Internet archive keeps copies of older versions of websites. And books, movies and music all free.(If your favorite website has disappeared find it again on the archive)

Enter the name of a website to see its history.

for movies try out frames of reference

Light lecture powerpoint. light powerpoint


Three little pigments

Circular keyboard

and my lesson

Color mixing

Mass vs radius for everything in the universe




Cow Eye Disection


Electronic versions of Summer Shop Projects


Distortion of spacetime by mass (gravity) is described here:

My article in the magazine of Fantasy and Science Fiction are here:

Here is the article "General Relativity at Home"

And here is the article about "Bicycling at the speed of light"

Here is the image of the big bang

wmap big bang

An image of the big bang with temperature coded by color red = warm blue = cold.( the range of temperatures is 200 microdegrees Kelvin)

Here is the angular frequency spectrum of the temperature variations.

This was taken by the Wilkinson Macrowave anisotropy project. 

We have a Teacher Institute Facebook page. Search Facebook for Exploratorium Teacher Institute.

Geoff Gould has posted images of class on this website.



Here are some light activities

Peel a CD, cut the aluminizing off a compact disk to make a transmssion diffraction grating.

Color Diffraction Grating, use a diffraction grating to observe the spectra of colors.

Image on a Mirror make an image on the surface of a mirror.

Fresnel lens and Laser trace laser paths through a lens.

Scan a Laser through a lens scan a lser across a lens.

Laser CD, reflect a laser off a CD to measure the line spacing of the

Laser Light, Explore the properties of laser light.

Laser Milk, Laser light scattered through milk produces a 3-d time varying interference pattern

Light Box, build a simple box to explore image making

Poisson Spot, make one with a pointer laser and a BB

Ray Tracing, How to do it

Audacity is a free sound recording program with spectrum analysis and automatic musical note identification.


San Francisco 1906 earthquake movie

Seeing Yellow (Disagreeing about color) the Snack pdf format an article by Gorazd Planinsic.

The spectra of the elements


Air resistance force calculation. Why is air friction proportional to v^2 for turbulent airflow.

Information about human senses:

Howard Hughes Medical Institute, Seeing Hearing and Smelling the world.

A great source of physics information

Hyper Physics

A source of physics data.  Wolfram Alpha

Perception Videos

Men carrying a door between two people videos:



Find the Highest Note

Laser Speckle explanation


We purchase our colored filters from Holtz-Muller theater supply in San Francisco, #415-826-8383

They are $6.50 per sheet, 20 x 24 inches

TI uses Roscolux Medium Red #27

Roscolux #80 Primary Blue, and

Lee Filters #139 Primary Green.

Mix and Match

Add R G B to make other colors

Phosphorescent Vinyl

From educational innovations

Difraction grating

From Project Star

Air Resistance

Air resistance F = kv vs cv^2

For laminar flow the force from air resistance is proportional to the velocity.

For turbulent flow it is proportional to velocity squared.

A bicyclist travelling at velocity v in still air experiences air friction that increases as the velocity of the bicyclist squared. F = cv^2

Let's do a simpler problem first the bicyclist colldes with a beanbag of mass m. As viewed by the bicyclist the beanbag is mving towards them and has kinetic energy E = 0.5mv^2 which goes to 0 in the inelastic collision with the byciclist. So in the inelastic collision between beanbag and bicyclist the bicyclist must do work on the beanbag to bring it to rest. The work done will be 0.5mv^2. Work is force times distance. So the force of hitting one beanbag depends on the distance over which the beanbag is brought to rest. 0.5mv^2 = F d.

Now consider a beanbag every metre, d = 1m. And calculate an average force by assuming it takes the full meter to stop the beanbag.

F = E/d = 0.5 mv^2 = Fd   so F = 0.5mv^2/d


Consider air of density p moving at velocity v colliding with an object with a front surface area A.

The air comes to rest when it strikes the object. The mass of air is pV  where V is the volume of air that hits the cyclist.

So the kinetic energy, E,of the air is 0.5mv^2 = 0.5 pVv^2 now the volume of air is Ad  so we get

E = 0.5pAdv^2

and F = E/d = 0.5 pAv^2

the air resistance force is proportional to the density of the air, the area of the bicyclist and the velocity of the bicyclist squared.


Scientific Explorations with Paul Doherty

© 2010

21 June 2010