Teacher Notes



Transverse WaveDemonstration Kit
Publication No. 12007
IntroductionHow are wavelength and frequency related in a transverse wave? This demonstration allows your students to visualize the relationship between wavelength and frequency. Concepts
MaterialsLine Pattern Master*
Line Pattern Transparency* Marker, red, permanent or transparency Overhead projector and screen Scissors, 1 per student (optional) Tape Wave Pattern Master* Wave Pattern Transparency* *Materials included in kit. Safety PrecautionsAlthough this demonstration is considered nonhazardous, please follow normal laboratory safety guidelines. Handle sharp cutting devices with care. DisposalThe materials may be saved for future demonstrations. Prelab Preparation
Procedure
Student Procedure (Optional)
Student Worksheet PDFTeacher Tips
Correlation to Next Generation Science Standards (NGSS)^{†}Science & Engineering PracticesDeveloping and using modelsPlanning and carrying out investigations Using mathematics and computational thinking Disciplinary Core IdeasMSPS4.A: Wave PropertiesHSPS4.A: Wave Properties Crosscutting ConceptsPatternsSystems and system models Stability and change Performance ExpectationsHSPS41. Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media. DiscussionAll electromagnetic radiation travels at the same constant speed through a vacuum. This constant speed is known as the speed of light and is designated with the symbol c, where c = 2.998 x 10^{8} m/s in a vacuum. Experiments have shown that electromagnetic radiation travels in a similar fashion to that of water waves in a ripple tank or pond—that is, electromagnetic radiation travels in the form of waves, more specifically transverse waves. A transverse wave is described as a wave in which the disturbance of the wave pattern travels at a right angle to the direction of motion of the wave. Conversely, for a longitudinal wave (also known as a compression wave), the wave pattern disturbance travels along the same direction as the direction of motion of the wave. Sound waves are examples of longitudinal waves (see Figure 1). {12007_Discussion_Figure_1}
Reminiscent of all waves, electromagnetic waves have a wavelength, frequency, speed, and an amplitude (see Figure 2). The relationship between the wavelength and the frequency of a wave is determined by the speed of the wave (the speed of light for electromagnetic waves) according to the equation below. {12007_Discussion_Figure_2}
c = λ c is the speed of light (speed of the wave) λ is the wavelength of the wave (Greek letter lambda) ν is the frequency of the wave (Greek letter nu) It can be seen from the equation that as electromagnetic radiation wavelength decreases, the frequency must increase. This relationship between frequency and wavelength is called an inverse relationship. This demonstration illustrates this inverse relationship between the frequency and the wavelength for waves that travel at the same speed. The three wave patterns provided (A, B and C) have three different wavelengths, 1½", 3" and 4½", respectively. The red mark in each wave image represents the wave front (the leading edge of the wave). As the line pattern is moved over the wave patterns, the red mark travels at the same lengthwise speed which shows that the three wave fronts are traveling at the same speed. By observing the red mark in each wave pattern, it can be seen that the red mark in the smaller wavelength waveform, A, “travels” up and down much more frequently than for the longer wavelength patterns (B and C). The transverse motion is quicker for the smaller wavelength wave—it has a higher frequency. More specifically, every time the red mark travels an entire wavelength in the longer wavelength waveform (C), the red mark travels up and down a total of three times in the smallest wavelength waveform (A). Waveform A’s wavelength is three times smaller than waveform C’s wavelength, and therefore the frequency of A must be three times faster than C, because the waves are traveling at the same speed. ReferencesFlinn Scientific would like to thank George Gross from Union High School (retired), Union, New Jersey, and George Hague from St. Mark’s School, Dallas, Texas, for providing us with this wave principle demonstration. Recommended Products

