Examples of spectral radiance in the following topics:
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- where $B$ is the spectral radiance of the surface of the black body, $T$ is its absolute temperature, $\lambda$ is wavelength of the radiation, $k_B$ is the Boltzmann constant, $h$ is the Planck constant, and $c$ is the speed of light.
- Note that the spectral radiance depends on two variables, wavelength and temperature.
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- This process produces an emission spectrum of x-rays at a few discrete frequencies, sometimes referred to as the spectral lines.
- The spectral lines generated depend on the target (anode) element used and therefore are called characteristic lines.
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- If the range of the power-law distribution is sufficiently large (at least an order of magnitude) we can take $x_1\rightarrow 0$ and $x_2 \rightarrow \infty$ in (23) so that the integral is simply a constant and we find that the spectral distribution is also a power-law $\omega^{-s}$ with a power-law index of $s=(p-1)/2$.
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- Notice that the spectral index does not depend on the power-law index of the particle distribution but rather results from the power-law relationship between particle energy and frequency.
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- Colors that can be produced by visible light of a narrow band of wavelengths (monochromaticlight) are called pure spectral colors.
- Quantitatively, the regions of the visible spectrum encompassing each spectral color can be delineated roughly as:
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- The hydrogen spectrum had been observed in the infrared (IR), visible, and ultraviolet (UV), and several series of spectral lines had been observed .
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- Relating the spectral lines and their strengths to particular atoms are their abundances requires a detailed knowledge of the physics of atoms (Chap.8) and their transitions (Chap.9).