(A) : At frequencies above 40 MHz, communication is essentially limited to line of sightpath.
(R) : At these frequencies, the antenna is relatively smaller and can be placed at heights of many of wavelengths above the ground.

Options

A. Both 'A' and 'R' are true and 'R' is the correct explanation of 'A'.
B. Both 'A' and 'R' are true and 'R' is not the correct explanation of 'A'.
C. A' is true abd 'R' false
D. A' is false and 'R' is false

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided:

### Step 1: Analyze the Assertion (A)
The assertion states: "At frequencies above 40 MHz, communication is essentially limited to line of sight path."

- **Explanation**: This statement is true. At frequencies above 40 MHz, the wavelength of the electromagnetic waves becomes shorter, which means they do not propagate well over long distances through reflection or diffraction. Instead, they require a direct line of sight between the transmitter and receiver to ensure effective communication.

### Step 2: Analyze the Reason (R)
The reason states: "At these frequencies, the antenna is relatively smaller and can be placed at heights of many wavelengths above the ground."

- **Explanation**: This statement is also true. At higher frequencies, the size of the antenna is smaller relative to the wavelength, which allows for easier installation at greater heights. However, while this statement is true, it does not provide a justification for why communication is limited to line of sight.

### Step 3: Conclusion
- Both the assertion (A) and the reason (R) are true.
- However, the reason (R) does not correctly explain the assertion (A). The limitation to line of sight communication is due to the behavior of electromagnetic waves at higher frequencies, not merely because of the size of the antennas.

### Final Answer
Both A and R are true, but R is not the correct explanation of A.

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