A slide having green and cyan segments superposed on a red background, is projected onto a screen. Chromatic aberration in the eye diffuses the boundary between any of the two pairs of colors, causing a blurry white or gray line at the boundary.

These colors were chosen because they are complements as seen by various eyes. One or both of the pairs of colors will mix to form white when viewed by virtually anyone's eyes. The colors are not quite correct in the photograph above.

A meter stick is held by one person directly above the hands of a second person, the victim. When the meter stick is dropped, the victim closes its hands to catch the meter stick. The reaction time T of the victim can be calculated as T=SQRT(2S/g), where g is the acceleration of gravity and S is the distance the meter stick has fallen.

The experiment is then repeated with the room darkened. Typically the meter stick will fall considerably further, due to the longer reaction time in a darkened environment. The increased time, due to visual latency, can be determined by subtracting the reaction time in the light from that in the dark.

This is one reason for increased reaction time in night driving.

Allow the mercury lamp 5-10 minutes to warm up, then remove the covers from the lamp and the PE tube. For each frequency filter, adjust the input stopping voltage from the tunable power supply until the current measured on the the current amplifier reaches 0.

Plot the five frequencies (c/wavelength) vs the voltage, and the slope should be h/e. By assuming a standard value for e, h can be computed, or vice versa.

Collimated light from a laser diode is incident on a double slit, creating interference. A photomultiplier tube sensitive to single photons is attached to the rotating telescope of the spectroscope opposite the light source. The signals from the tube are seen on the oscilloscope and heard using an audio amplifier and loudspeaker.

As the photon counter is slowly rotated the intensity of photons traces out the interference pattern for the double slit used. An identical slide on the Laser Cart (Demonstration M1-11) can be used to display the double slit interference pattern.

The double slit used has slit width of 0.04mm and slit spacing of 0.250mm. With the single photon counter you can hear about nine interference maxima in the main diffraction maximum, pass through the diffraction minima on either side, and hear a few interference maxima in the second diffraction maximum, as seen in the photograph above.

Place the clean projection tray on the overhead projector with the ruler underneath. Cover the tray with a layer of water (over 1/8") and allow the water to settle. Lightly dust the surface with lycopodium powder, and adjust the projector so the powder and ruler are both in focus (center photograph). Hold the dropper just above the center of the tray and carefully release one drop of oleic acid solution onto the water surface. A circular "hole" quickly appears in the powder film, reaching its fixed maximum diameter in a few seconds (photograph at right). This is the monomolecular layer of oleic acid molecules held together by surface tension. Measure the diameter of the film so that the approximate thickness can be determined.

The following comments on the nature of oleic acid that makes this experiment possible were taken from the Science Teachers' Resource Center, Chemistry section, laboratory #31.

Molecules that are repelled by water are called hydrophobic. Molecules that are attracted to water are called hydrophilic. Cooking oil is hydrophobic; it won't mix with water. Some molecules have one end that is hydrophobic and one end that is hydrophilic. There are such molecules in the cells in your body. They are used to take hydrophobic nutrients into the cell that is mostly water. Soaps are this way also so that they can dissolve both hydrophobic and hydrophilic substances and be washed away by water.

Oleic acid is a substance with one hydrophobic and one hydrophilic end. When a small amount of oleic acid is placed on the surface of water, it stands on end with the hydrophilic end towards the water and the hydrophobic end away. If you could see them, they would look like fans at a crowded concert.

In this lab, we will find the length of one oleic acid molecule by spreading a small amount over the surface of water and measuring the diameter of the circle. The oleic acid spreads itself into a one-molecule thick layer in the shape of a VERY flat cylinder.

Read more: Determination of the Size of a Fatty Acid Molecule, by David A. Katz is a very nice article on the web describing this experiment. (pdf)

Optionally, a light source can be provided with different coulour filters. The light source provides a photon of energy. With a red filter the ball jumps one step; with the blue filter the electron jumps two or three steps up the ladder. Radiation with the wrong light, say green light, leaves the ball in its ground state (on the floor), because that energy would leave the ball between energy levels. Invite students to make predictions about the results of different colours of light/different amounts of absorbed energy.

A piece of tissue paper is placed on a screen mesh over the input port of a vacuum cleaner. After the air is sucked through the vacuum cleaner for about 15 minutes (depending on how much radon gas is present) the tissue is placed by the window of a Geiger tube. In a radon-rich environment, the increased count rate would be clearly evident, showing that radioactive materials are on the tissue. This count rate can be contrasted with the count rate of a clean piece of the same tissue paper.

The radioactivity results from radioactive decay products of radon gas which are solids and attach themselves to dust particles in the air. The tissue removes these dust particles as the air is sucked through the vacuum cleaner.

Also included are a home-type radon testing kit along with copies of the descriptive literature.

This demonstration is provided primarily for illustrative purposes, and will not reliably detect radon in the classroom environment.

Since we cannot easily create a long duration microgravity environment in the classroom, this demonstration instead models this effect with the expansion being caused by a change in air pressure. A column of discs is separated by marshmallows, and the whole placed into a vacuum chamber. As the pressure is reduced, the gas in the marshmallows expands, forcing apart the spinal discs. When pressure returns, the spine collapses back, much like astronauts experience when they return to Earth.

Challenge your students to think of other body parts and processes that could be similarly affected by changes in gravity.

Force applied by the biceps , pulling up with the hand: Apply 2.5 kg to the biceps cable to support the unloaded forearm. The forearm may be kept at equilibrium by the simultaneous addition of masses in the ratio of 10:1 at the biceps and at the hand. The torques are balanced almost independently of the angular position of the arm.

Force applied to the triceps, pushing down with the hand: Hang the spring scale between the top hook and the hand hook, and attach the hanger to the triceps cable. Add masses to the hanger to determine how much force in the triceps is necessary to push down with the force read on the scale.