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Chapter 32 Physics: Waves and Electromagnetic Radiation

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Termini in questo insieme (16)

  • What is the letter and unit for angular frequency?
    Angular frequency is represented by \(\omega\) and measured in radians per second (rad/s).
  • What is the letter and unit for wave number?
    Wave number is represented by \(k\) and measured in inverse meters (1/m).
  • What is the speed of light and its unit?
    The speed of light is \(c=3.00\times10^{8}\) meters per second (m/s).
  • What is the Poynting vector and its unit?
    The Poynting vector is represented by \(S\) and measured in watts per square meter (W/m²).
  • What is intensity and its unit?
    Intensity is represented by \(I\) and measured in watts per square meter (W/m²).
  • Write down the wave equation relating speed, frequency, and wavelength.
    The wave equation is \(v=f\lambda\), where v is speed, f is frequency, and \(\lambda\) is wavelength.
  • What is the equation for the length of a cavity for a standing wave?
    The length L of the cavity is related to wavelength by \(L=\frac{n\lambda}{2}\), where n is an integer.
  • Write the definitions of angular frequency and wave number.

    Angular frequency: \(\omega=\frac{2\pi}{T}\); Wave number: \(k=\frac{2\pi}{\lambda}\).

  • What is the relation between electric and magnetic fields in an EM wave?
    The electric field E and magnetic field B relate as \(E=cB\), where c is the speed of light.
  • Write the equation relating the speed of light to universal constants.
    The speed of light is \(c=\frac{1}{\sqrt{\varepsilon_0\mu_0}}\), where \(\varepsilon\)_0 is permittivity and \(\mu\)_0 is permeability of free space.
  • Write the equation defining the Poynting vector.
    The Poynting vector is \(\mathbf{S}=\frac{1}{\mu_0}\mathbf{E}\times\mathbf{B}\), representing energy flow per unit area.
  • Describe the directional relationship between \(S\), \(E\), and \(B\) in an EM wave.
    \(S\) points in the direction of wave propagation; \(E\) and \(B\) are perpendicular to \(S\) and to each other.
  • Write the equation that defines intensity.
    Intensity is \(I=\frac{Energy}{Time\cdot Area}\), the power per unit area.
  • What are the names and units of the quantities P, p, and P (different symbols)?
    P: power in watts (W); p: momentum in kilogram meters per second (kg·m/s); P (pressure): pressure in newtons per square meter (N/m²).
  • Write the equation for radiation pressure when light is absorbed.
    Radiation pressure for absorbed light is \(P=\frac{I}{c}\), where I is intensity and c is speed of light.
  • Write the equation for radiation pressure when light is reflected.
    Radiation pressure for reflected light is \(P=\frac{2I}{c}\), twice that of absorbed light.