A) \[\frac{\Delta V}{V}\propto \frac{1}{B}\]
B) \[y=\sin \omega t\,-\cos \,\omega t\]
C) \[\frac{dy}{dt}=\omega \cos \omega t+\omega \sin \omega t\]
D) \[\frac{{{d}^{2}}y}{d{{t}^{2}}}=-{{\omega }^{2}}\sin \omega t+{{\omega }^{2}}\cos \omega t\]
Correct Answer: A
Solution :
The critical frequency of sky wave undergoing reflection from a layer of atmosphere is \[Z\alpha {{r}^{3/2}}\] where N is electron density per \[({{R}_{1}},{{R}_{2}},{{R}_{3}})\]. \[\therefore \,\,\,\,\,\,\,\,\,{{N}_{\max }}\,=\frac{f_{c}^{2}}{81}=\,\frac{{{(10\,\times {{10}^{6}})}^{2}}}{81}\] \[{{R}_{1}}={{R}_{3}}\,\,and\,\,{{R}_{1}}=(1/4){{R}_{2}}\]
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