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A wave has angular frequency 30 rad/s and wavelength \(2.0 \mathrm{m}\) What are its (a) wave number and (b) wave speed?

Short Answer

Expert verified
The wave number of the wave is \(0.5 rad/m\) and its speed is \(9.54 m/s\).

Step by step solution

01

Calculate the wave number

The wave number \(k\) of a wave is the reciprocal of the wavelength \(\lambda\). Therefore, \(k = 1/\lambda\). Substitute \(\lambda = 2.0 m\) into the equation to get: \(k = 1/2.0 m = 0.5 rad/m\).
02

Convert angular frequency to frequency

The angular frequency \(\omega\) is related to the frequency \(f\) of the wave by the equation \(\omega = 2\pi f\). Therefore, \(f = \omega / (2\pi)\). Substitute \(\omega = 30 rad/s\) into the equation to get: \(f = 30 rad/s / (2\pi) = 4.77 Hz\).
03

Calculate the wave speed

The wave speed \(v\) is the product of wavelength \(\lambda\) and frequency \(f\). Therefore, \(v = \lambda f\). Substitute \(\lambda = 2.0 m\) and \(f = 4.77 Hz\) into the equation to get: \(v = 2.0 m * 4.77 Hz = 9.54 m/s\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Angular Frequency
Angular frequency, denoted by \( \omega \), is a measurement of how fast something oscillates in a circular motion or wave pattern. Think of it like a speedometer for waves, telling you how many cycles occur in a unit of time. It is measured in radians per second (rad/s).
- For a wave, angular frequency is related to the frequency \( f \), the number of cycles per second. They are connected by the formula: \( \omega = 2\pi f \). - This relationship shows that angular frequency is just the frequency scaled by \( 2\pi \), which corresponds to one full rotation in radians.
Understanding angular frequency is key to grasping wave phenomena. Once you know it, you can easily find other properties of the wave, such as the wave speed when combined with the wavelength.
Wavelength
Wavelength, represented by the Greek letter \( \lambda \), is the distance over which a wave's shape repeats. It's like measuring the length of one full wave cycle, from crest to crest or trough to trough. - The unit of wavelength is meters (m), indicating it measures a linear distance.
- In the context of our specific problem, we were given a wavelength of \( 2.0 \mathrm{m} \) for the wave.
Wavelength is an essential property in determining how waves behave and interact with the environment. It helps, for instance, in figuring out the wave number, which we'll discuss next.
Wave Number
The wave number \( k \) is an important concept related to wavelength, effectively showing the number of wave cycles within a unit distance. It’s like a measure of wave density in space.
- The wave number is given by \( k = \frac{1}{\lambda} \), making it the inverse of the wavelength.
- In our exercise, using a wavelength of \( 2.0 \mathrm{m} \), we found the wave number to be \( k = 0.5 \mathrm{rad/m} \).
Wave numbers are crucial in fields such as optics and acoustics. They help describe how waves propagate through different media, linking directly with the wave speed when considered alongside the angular frequency.
Wave Speed
Wave speed \( v \) is about how fast a point on the wave, like a crest, travels through space. It's an essential characteristic because it represents the movement of energy.
- To find wave speed, you multiply the wavelength \( \lambda \) by the frequency \( f \): \( v = \lambda f \).
- For the wave in our exercise, we used a wavelength of \( 2.0 \mathrm{m} \) and a frequency of \( 4.77 \mathrm{Hz} \), calculated from the angular frequency, resulting in a wave speed of \( 9.54 \mathrm{m/s} \).
Wave speed ties the other concepts together into a real-world application, showing how different wave parameters interchangeably affect the motion of the wave.

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Most popular questions from this chapter

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