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--- un:band [2024/04/16 02:10] – asad
+++ un:band [2024/04/16 02:28] (current) – asad
@@ Line 1: / Line 1: @@
 ====== Bands ======
-Color or frequency bands are standardized systems of filters in astronomy which are very different for different frequency ranges. In the visibile range, the bands are usually called //spectral color bands// or //photometric bands// or //photometric systems//.
+Color or frequency bands are standardized systems of filters in astronomy which are very different for different frequency ranges. In the visibile range, the bands are usually called //spectral color bands// or //photometric bands// or //photometric systems//. In radio they are called //frequency bands// each of which are made of narrower //frequency channels//.
 ===== - Photometric system =====
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 {{:un:ubvri.webp?nolink&600|}}
-As evident from the figure, the U filter only allows ultraviolet light, the B filter blue light and V yellow-green light. In the Johnson-Cousins-Glass (JCG) system more filters are added. In the following table, we show the effective wavelength $\lambda_e$, effective frequency $\nu_e$, the FWHM passbands $\Delta\lambda$ and $\Delta\nu$, and the spectral flux density at magnitude $m=0$ at $\nu_e$ in units of jansky ([[Jy]]) for each of the filters in the JCG system (Bradt, AM).
+As evident from the figure, the U filter only allows ultraviolet light, the B filter blue light and V yellow-green light. In the Johnson-Cousins-Glass (JCG) system more filters are added. In the following table, we show the effective wavelength $\lambda_e$, effective frequency $\nu_e$, the FWHM passbands $\Delta\lambda$ and $\Delta\nu$, and the spectral flux density at magnitude $m=0$ at $\nu_e$ in units of jansky (Jy) for each of the filters in the JCG system (Bradt, AM).
 ^ Filter ^ $\lambda_e$ (nm) ^ $\Delta\lambda$ (nm) ^ $\nu_e$ (THz) ^ $\Delta\nu$ (THz) ^ $S_0$ (Jy) ^
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 | L | 3450 | 472 | 87 | 11.9 | 281 |
 | M | 4750 | 460 | 63 | 6.1 | 154 |
+===== - Radio bands =====