In communication system, only one percent frequency of signal of wavelength 900 nm can be used as band width. How many channel of 6MHz band width can broadcast this? $\left(c=3\times {10}^{8}m/s, h=6.6\times {10}^{-34}J-s\right)$

$$\begin{gathered} Here signal wavelength, \lambda =900nm=9\times {10}^{-7}m \\ Frequency of source is \\ f=\frac{c}{\lambda }=\frac{3\times {10}^8}{9\times {10}^{-7}}=3.33\times {10}^{14}Hz \\ \therefore Total band width used for communication= 1 \% of 3.33\times {10}^{14}Hz =3.33\times {10}^{12} \\ So, number of channels for signals =\frac{total bandwidth available for communication}{bandwidth of T.Vsignal} \\ =\frac{3.33\times {10}^{12}}{6\times {10}^6}=5.55\times {10}^5 \end{gathered}$$