Assertion: Long distance communication between two points on the earth is achieved using sky waves.
Reason: sky wave propagation takes place above. The frequency of 30 MHz.

Options

A. Both A and R are true and R is correct explaination of A
B. A is true but R is wrong
C. A is wrong but R is true
D. Both are wrong

Explanation

To solve the assertion and reasoning question, we will analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states: "Long distance communication between two points on the earth is achieved using sky waves."

- **Explanation**: Sky wave propagation is a method of radio communication that utilizes the ionosphere to reflect radio waves back to the earth. This allows for long-distance communication because the waves can travel beyond the horizon by bouncing off the ionosphere.

### Step 2: Analyze the Reason
The reason states: "Sky wave propagation takes place above the frequency of 30 MHz."

- **Explanation**: This statement is incorrect. Sky wave propagation typically occurs for frequencies between 3 MHz and 30 MHz. Frequencies above 30 MHz generally do not utilize sky wave propagation; instead, they are more suited for space wave propagation, which travels in a straight line and does not rely on reflection from the ionosphere.

### Step 3: Conclusion
Now we can conclude the relationship between the assertion and the reason:

- The assertion is **true** because sky waves are indeed used for long-distance communication.
- The reason is **false** because sky wave propagation does not occur above 30 MHz; it is effective for frequencies up to 30 MHz.

### Final Answer
Thus, the correct answer is: **A is true but R is wrong (Option B).**

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