### Waves, sound, and light

• #### Additive Colors

Control the intensity of red, green, and blue spotlights. Additive colors can be observed where the spotlights overlap. The RGB value of any point can be measured. Just about any color can be created by mixing varying amounts of red, green, and blue light.

• #### Basic Prism

Shine white light or a single-color beam through a prism. Explore how a prism refracts light and investigate the factors that affect the amount of refraction. The index of refraction of the prism, width of the prism, prism angle, light angle, and light wavelength can be adjusted.

• #### Doppler Shift

Observe sound waves emitted from a moving vehicle. Measure the frequency of sound waves in front of and behind the vehicle as it moves, illustrating the Doppler effect. The frequency of sound waves, speed of the source, and the speed of sound can all be manipulated. Motion of the vehicle can be linear, oscillating, or circular.

• #### Doppler Shift Advanced

Derive an equation to calculate the frequency of an oncoming sound source and a receding sound source. Also, calculate the Doppler shift that results from a moving observer and a stationary sound source. The source velocity, sound velocity, observer velocity, and sound frequency can all be manipulated.

• #### Hearing: Frequency and Volume

Test your hearing range by listening to low-, medium-, and high-frequency sounds. Compare the relative loudness of sounds at each frequency to create an equal-loudness curve. In a quiet room, measure your threshold of audibility for each frequency, and compare your results to others. The volume of each sound can be adjusted.

• #### Herschel Experiment

Shine sunlight through a prism and use a thermometer to measure the temperature in different regions of the spectrum. The thermometer can be dragged through the visible spectrum and beyond. This recreates the experiment of William Herschel that led to the discovery of infrared radiation in 1800.

• #### Herschel Experiment

Shine sunlight through a prism and use a thermometer to measure the temperature in different regions of the spectrum. The thermometer can be dragged through the visible spectrum and beyond. This recreates the experiment of William Herschel that led to the discovery of infrared radiation in 1800.

• #### Laser Reflection

Point a laser at a mirror and compare the angle of the incoming beam to the angle of reflection. A protractor can be used to measure the angles of incidence and reflection, and the angle of the mirror can be adjusted. A beam splitter can be used to split the beam. Both plane and irregular mirrors can be used.

• #### Longitudinal Waves

Observe the propagation of longitudinal (compression) waves in a closed or open tube with evenly-spaced dividers. The strength and frequency of the waves can be manipulated, or waves can be observed as individual pulses. Compare the movement of dividers to graphs of displacement, velocity, acceleration and pressure.

• #### Penumbra Effect

Observe the partial shadows cast by a rectangular block lit by multiple light sources. The number of light sources ranges from one to five, and individual lights can be turned on or off. The light spacing, block width, and distance from the lights to the block can be varied. Light intensity can be observed on a detector.

• #### Phased Array

Observe the wave fronts produced by four closely-spaced emitters. The spacing and phase shift of each wave source can be adjusted, as well as the wave velocity. With all four sources you can observe a region of constructive interference that moves over time. The phased array has several real world applications such as radar and ultrasound.

• #### Ray Tracing (Lenses)

Observe light rays that pass through a convex or concave lens. Manipulate the position of an object and the focal length of the lens and measure the distance and size of the resulting image.

• #### Ray Tracing (Mirrors)

Observe light rays that reflect from a convex or concave mirror. Manipulate the position of an object and the focal length of the mirror and measure the distance and size of the resulting image.

• #### Refraction

Determine the angle of refraction for a light beam moving from one medium to another. The angle of incidence and each index of refraction can be varied. Using the tools provided, the angle of refraction can be measured, and the wavelength and frequency of the waves in each substance can be compared as well.

• #### Ripple Tank

Study wave motion, diffraction, interference, and refraction in a simulated ripple tank. A wide variety of scenarios can be chosen, including barriers with one or two gaps, multiple wave sources, reflecting barriers, or submerged rocks. The wavelength and strength of waves can be adjusted, as well as the amount of damping in the tank.

• #### Sound Beats and Sine Waves

Listen to and see interference patterns produced by sound waves with similar frequencies. Test your ability to distinguish and match sounds as musicians do when they tune their instruments. Calculate the number of "sound beats" you will hear based on the frequency of each sound. [Note: Headphones are recommended for this Gizmo.]

• #### Subtractive Colors

Move spots of yellow, cyan, and magenta pigment on a white surface. As the colors overlap, other colors can be seen due to color subtraction. The color of most things you see--such as cars, leaves, paintings, houses, and clothes--are due to color subtraction. The intensity of the cyan, magenta, and yellow can be adjusted, and the RGB value at any location can be measured.

• #### Waves

Observe and measure transverse, longitudinal, and combined waves on a model of a spring moved by a hand. Adjust the amplitude and frequency of the hand, and the tension and density of the spring. The speed and power of the waves is reported, and the wavelength and amplitude can be measured.