NTA Abhyas 2020
- Exam
- NTA Abhyas
- Year
- 2020
- Subject
- Physics
- Chapter
- Communication System
NTA Abhyas 2020 · Physics · Communication System
The maximum frequency for reflection of sky waves from a certain...
The maximum frequency for reflection of sky waves from a certain layer of the ionosphere is found to be {f}_\max = 9 ( {N}_\max{)}^{1 / 2}, where {N}_\max is the maximum electron density at that layer of the ionosphere. On a certain day, it is observed that signals of frequencies higher than are not received by reflection from the layer of the ionosphere. Estimate the maximum electron densities of the & layers on that day.
Options
- A
- B
- C
- D
Correct answer
A.
Step-by-step solution
The maximum frequency for reflection of sky waves {f}_\max=9 ( {N}_\max{)}^{1 / 2} where {N}_\max is a maximum electron density. For F_{2} layer, {f}_\max=8MHz So, 8 \times {10}^{6}=9 ( {N}_\max{)}^{1 / 2} maximum electron density,{N}_\max=\left(\dfrac{8 \times {10}^{6}}{9}\right)^{2}=7 \cdot 9 \times {10}^{11}m^{- 3}