Question

In the following question from statement-1 (Assertion) is followed by statement-2 (Reason) Each question has the following four choice out of which only one choice is correct (a) Statement- 1 is true, statement \(-2\) is true. Statement \(-2\) is a correct explanation for statement-1. (b) Statement-1 is true, statement-2 is true, statement-2 is not a correct explanation for statement-1. (c) Statement- 1 is true, statement \(-2\) is false (d) Statement-1 is false, statement \(-2\) is true. Statement-1 :- sky wave communication is not suitable for frequencies greater than \(30 \mathrm{MHz}\). Statement \(-2:-\) High frequency signals die out before reaching the ionosphere. (A) a (B) \(b\) (C) \(c\) (D) \(\mathrm{d}\)

Short answer

The short answer is: (c) Statement- 1 is true, statement -2 is false.

Step-by-step solution

: We need to first comprehend the meaning and context of the two statements. Statement-1: Skywave communication is not suitable for frequencies greater than 30 MHz. Skywave communication is a method for transmitting radio signals by bouncing them off the ionosphere back to the Earth. The statement is implying that this communication technique is not suitable for frequencies above 30 MHz. Statement-2: High-frequency signals die out before reaching the ionosphere. This statement suggests that signals with higher frequencies are unable to reach the ionosphere and thus cannot be reflected back to Earth for sky wave communication. #Step 2: Determine the truth of each statement#

: Now that we have understood the context and meaning of both statements, we need to verify whether each statement is true or false. Statement-1: True. Skywave communication is limited to frequencies below 30 MHz because at higher frequencies, signals penetrate the ionosphere, and are not reflected back to Earth. Statement-2: False. The reason for the limitation of sky wave communication to frequencies below 30 MHz is not that high-frequency signals die out before reaching the ionosphere. The actual reason is that the higher frequency signals penetrate the ionosphere instead of being reflected, making them unsuitable for sky wave communication. #Step 3: Analyze the relationship between the statements#

: As we have verified the truth or falsehood of the statements, now we will analyze their relationship. That is, we need to determine if Statement-2 is a correct explanation for Statement-1. Since Statement-2 is false, it cannot be a correct explanation for the true Statement-1. #Step 4: Select the best answer option#

: Based on the analysis in Step 3, we will now choose the appropriate answer option: (a) Statement- 1 is true, statement -2 is true. Statement -2 is a correct explanation for statement-1. (b) Statement-1 is true, statement-2 is true, statement-2 is not a correct explanation for statement-1. (c) Statement- 1 is true, statement -2 is false (d) Statement-1 is false, statement -2 is true. The correct answer is (c) Statement- 1 is true, statement -2 is false.

Key concepts

Skywave Communication

Skywave communication is an exciting technology that allows us to communicate over long distances. Unlike typical line-of-sight communication methods, skywave communication uses the ionosphere as a reflective surface to bounce radio waves back to Earth. This technique is particularly useful for sending signals across the globe without relying on satellite technology or extensive cabling.

• This method primarily applies to shortwave radio communications.
• Skywave communication can effectively cover great distances that range from hundreds to thousands of kilometers.
• It is often used for international broadcasting, amateur radio, and in some cases, military communications.

These radio waves hop to the ionosphere and are reflected back down, allowing them to travel beyond the horizon. However, it works best for certain frequency ranges, typically below 30 MHz. This is because higher frequency waves have different interactions with the ionosphere, which we will explore more below.

Ionosphere

The ionosphere is one of the Earth's layers, located approximately 30 to 600 miles above the Earth's surface. This layer is distinct due to its ability to reflect radio waves, which makes it instrumental in skywave communication. The presence of free electrons allows the ionosphere to reflect radio frequencies back to the Earth's surface.

• The ionosphere is influenced by solar radiation, meaning its characteristics can change depending on the time of day and solar activity.
• At night, the ionosphere is higher and more reflective, which can enhance long-distance communication.
• During the daytime, the ionosphere becomes denser and can absorb more radio waves, sometimes reducing the reach of skywave communication.

Different layers within the ionosphere, like the D, E, and F layers, offer varying reflective properties depending on the radio frequency used. Understanding the ionosphere's role helps us comprehend why some frequencies are more successfully bounced back than others.

Frequency Limits

Radio wave frequency is an essential factor in determining the effectiveness of skywave communication. The frequency of a wave influences its ability to travel, penetrate, or be reflected by the ionosphere. This is why skywave communication is more effective for frequencies below 30 MHz.

• Higher frequencies, typically above 30 MHz, tend to pass through the ionosphere rather than reflect off it.
• This phenomenon is mostly due to the ionosphere's density and its interaction with different frequencies.
• As a result, to maintain effective skywave communication, lower frequencies are preferred and more effective.

Because of these frequency limitations, technologies employing higher frequencies often rely on other methods like ground-wave propagation or satellite communications. By understanding their behavior relative to the ionosphere, engineers and technicians can select the optimal frequencies for communication systems across various applications.