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Inquiry: Waves

Purpose: To analyze the characteristics of waves.

Part 1 Procedure: Springs

Many waves move too fast or are too small to watch easily. But in a long "soft" spring you can make big waves that move slowly. To begin, use the spring hanging from the ceiling. Grasp the end of the spring and pull toward you and release. You will see a compression or a pulse move down the spring. In such a longitudinal wave the medium moves parallel to the direction of the wave. Next quickly move your hand at a right angle to the spring. You will see a crest travel down one side of the spring. In this transverse wave, the medium moves perpendicular to the direction of motion. Do the following and answer the discussion questions:

Inquiry Questions:

Using the slinky hanging from the ceiling:

  • Does the size of the crest change as it travels along the spring?

  • Does the reflected pulse return on the same side as you sent it?

  • What happens when you send two crests at each other at the same time in phase or out of phase with different or the same amplitudes?

  • Do the crests reflect off of each other or travel right through each other? (Hint: send a large amplitude wave towards a small amplitude wave)

  • As you generate waves at a higher frequency how does the wavelength change?

Using the slinky/hose have two people hold the ends of just the slinky on the floor:

  • Does stretching the spring have any affect on the velocity of the waves? (by stretching you are in effect changing the medium)

Now use the hose and spring.

  • What happens to a pulse when it hits the boundary between the hose and spring? Explain the effects of impedance change.

Part II Procedure: Waves in a Ripple Tank

Attempt to experiment and test everything we've learned about waves

Inquiry Questions:

  1. Describe phase change of reflection for fixed and free ends?

  2. What happens to the wavelength (shorten or lengthen) if you increase the frequency of a wave in a given medium?

  3. What happened to the wavelength (shorten, lengthen or remain the same) and frequency (increased, decreased or remain the same) as a wave traveled from the hose (low I) into the spring (high I)?

  4. What happens in terms of refraction as a straight water wave enters a shallower region at an angle to the normal line?

  5. What is diffraction and when does it happen the best?

  6. Describe the interference pattern (nodal and anti-nodal lines) in a 2-point system if the frequency is increased?

  7. Describe the interference pattern (nodal and anti-nodal lines) in a 2-point system if the points are brought closer together?

  8. How far is the distance in terms of wavelengths between a 1st node and a 5th node in a standing wave formation?

  9. Update your Google Waves Program to demonstrate interference.

  10. Update your Google Waves Program to demonstrate standing waves.