One string of a certain musical instrument is 75.0 cm long and has a mass of 8.75 g. It is being played in a room where the speed of sound is 344 m/s. (a) To what tension must you adjust the string so that, when vibrating in its second overtone, it produces sound of wavelength 0.765 m? (Assume that the break-ing stress of the wire is very large and isn't exceeded.) (b) What frequency sound does this string produce in its fundamental mode of vibration?
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Problem 13
Textbook Question
A carbon dioxide laser is an infrared laser. A CO2 laser with a cavity length of 53.00 cm oscillates in the m=100,000 mode. What are the wavelength and frequency of the laser beam?

1
The wavelength of the laser beam can be determined using the relationship between the cavity length and the mode number. For a standing wave in a laser cavity, the wavelength is given by: , where is the cavity length and is the mode number.
Substitute the given values into the formula: cm. Ensure the cavity length is in meters for consistency in SI units.
To find the frequency of the laser beam, use the relationship between the speed of light, wavelength, and frequency: , where is the speed of light (approximately m/s), is the wavelength, and is the frequency.
Rearrange the formula to solve for frequency: . Substitute the calculated wavelength and the speed of light into this equation.
Perform the calculations to determine the wavelength in meters and the frequency in hertz. Ensure all units are consistent throughout the process.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Laser Operation
Lasers operate on the principle of stimulated emission, where an excited atom or molecule releases a photon of light, which then stimulates other excited atoms to emit more photons. This process creates a coherent beam of light, characterized by its monochromaticity and directionality. In the case of a CO2 laser, the specific gas mixture and cavity design determine the wavelength and frequency of the emitted light.
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Wavelength and Frequency Relationship
Wavelength and frequency are inversely related properties of electromagnetic waves, described by the equation c = λf, where c is the speed of light, λ is the wavelength, and f is the frequency. This relationship indicates that as the wavelength increases, the frequency decreases, and vice versa. Understanding this relationship is crucial for calculating the wavelength and frequency of the laser beam based on its mode of oscillation.
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Mode of Oscillation
The mode of oscillation in a laser refers to the specific standing wave patterns that can form within the laser cavity. Each mode is characterized by a quantum number, which in this case is m=100,000 for the CO2 laser. The mode number helps determine the wavelength of the emitted light, as it relates to the length of the cavity and the number of wavelengths that fit within it, influencing the laser's output characteristics.
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