# Critical Frequency MCQ’s

This set of Antenna Multiple Choice Questions & Answers (MCQs) focuses on “Critical Frequency”.

1. What is the critical frequency when the electron density in the F1 layer is 20×1010/cm3?
a) 40.2GHz
b) 4.02 MHz
c) 40.2 MHz
d) 40.2Hz

2. What is the electron density of the layer if critical frequency is 3 MHz?
a) 11×1012/cm3
b) 0.11×1012/cm3
c) 1.1×1012/cm3
d) 0.11×1010/cm3

3. When a wave is incident normally then the acceptable highest frequency at which signal can be returned is the ______
a) critical frequency
b) LUF
c) optimum frequency
d) dominating frequency

4. For a regular layer, the critical frequency is proportional to the ______ of electron density.
a) Square
b) Inverse
c) Square root
d) Inverse square root

5. Which of the following frequency is greater than the critical frequency?
a) MUF
b) LUF
c) Optimum frequency
d) VLF

6. The value of refractive index when the MUF is equal to the critical frequency is ______
a) 1
b) 0
c) 0.5
d) 0.29

7. Find the critical frequency when the refractive index of the layer is 0.54 and MUF is 9MHz?
a) 0.84MHz
b) 7.57MHz
c) 0.75MHz
d) 8.4MHz

8. For fMUF ≥ fc, the wave will reflects back irrespective of the angle of incidence.
a) True
b) False

9. When the frequency decreases below _____ frequency, the signal reception becomes too weak and the Noise increases.
a) MUF
b) LUF
c) Optimum frequency
d) Critical frequency

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