What is the primary purpose of using a firewall on a Personal Computer?
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A.
To block unauthorised access and protect the computer
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B.
To clean up temporary files
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C.
To speed up internet connectivity
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D.
To increase storage space
Correct Answer:
A. To block unauthorised access and protect the computer
Explanation:
The absolute refractive index ($n$) of a medium is defined by the ratio $n = c/v$, where $c$ represents the speed of light in a vacuum and $v$ represents the speed of light (phase velocity) in that specific medium. If the refractive index is less than 1, it mathematically implies that the speed of light within that medium is greater than its speed in a vacuum ($v > c$). This phenomenon, known as anomalous refraction, occurs in specific conditions such as with X-rays, plasmas (like Earth's ionosphere), or near certain absorption frequencies. While the phase velocity can exceed $c$ in these cases, the group velocity—which carries information and energy—remains below the speed of light in a vacuum, consistent with the theory of relativity.
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