A) \[1.5\times {{10}^{10}}{{m}^{-3}}\]
B) \[1.24\times {{10}^{12}}{{m}^{-3}}\]
C) \[3\times {{10}^{12}}{{m}^{-3}}\]
D) none of these
Correct Answer: B
Solution :
The value of maximum frequency\[f\]which can be reflected from the layer at an angle of incidence i is given by \[{{f}^{2}}=\frac{80.6N}{{{\cos }^{2}}i}\] where\[i\]is angle of incidence and N is electron density. For the wave not reflected from ionosphere,\[i=0\] \[\therefore \] \[{{f}^{2}}=\frac{80.6N}{{{\cos }^{2}}{{0}^{o}}}=80.6\,N\] Or \[N=\frac{{{f}^{2}}}{80.6}=\frac{{{(10\times {{10}^{6}})}^{2}}}{80.6}\] \[=1.24\times {{10}^{12}}per\,\,{{m}^{-3}}\]
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