In this conceptual analogy question, Sound is related to Medium, so you must select the term that shows a similar scientific relationship with Light from the given alternatives.

Introduction / Context:

This question checks your basic understanding of physics concepts related to wave propagation. Sound waves require a material medium like air, water or solids to travel. Light, however, is an electromagnetic wave and behaves differently. The analogy "Sound : Medium" describes a necessary condition for the propagation of sound. You must identify which option completes the analogy by giving the correct essential condition or characteristic environment for light in a comparable way.

Given Data / Assumptions:

- Sound waves are mechanical vibrations that cannot travel in a perfect vacuum and require a medium such as air, water or solids.
- Light is an electromagnetic wave that does not require a material medium for propagation.
- Light can travel through vacuum as well as through media like air, water and glass, but its speed changes with the medium.
- The options are Air, Vacuum, Water, Glass and Space.

Concept / Approach:

The key difference is that sound needs a medium, whereas light does not. The relation "Sound : Medium" emphasises that a medium is essential for sound propagation. To create a parallel, we should use a word that captures the essential characteristic of light propagation. The most important fact is that light can travel through a vacuum, which is not possible for sound. Therefore, the most appropriate completion is "Light : Vacuum". This highlights the contrasting but equally fundamental condition for light, just as "medium" is fundamental for sound.

Step-by-Step Solution:

Verification / Alternative check:

We can verify by contrasting the situations. If all air is removed from a container to form a near vacuum, a ringing bell inside cannot be heard because sound cannot travel without a medium. However, if a light source is placed inside the same vacuum chamber, its light can still be seen outside through a transparent window, because light can travel through the vacuum. This thought experiment clearly supports the analogy "Sound : Medium :: Light : Vacuum". None of the other options directly express this defining property.

Why Other Options Are Wrong:

Air is indeed a medium for both sound and light, but the pair "Light : Air" would focus on one particular medium and not on the essential fact that light can travel without any medium.

Water is another medium that can transmit both sound and light, but it plays no unique or fundamental role for light propagation.

Glass is a transparent medium used in lenses and prisms, yet it is just one of many media and does not express the key contrast with sound.

Space is often used informally to refer to outer space, but scientifically the important concept is vacuum, which precisely indicates absence of material medium.

Common Pitfalls:

A common mistake is to select Air, since both sound and light frequently travel through air in daily life. However, analogy questions require the relationship to match at a conceptual level, not just based on common examples. Another pitfall is not recalling that sound cannot propagate in a vacuum, whereas light can, which is a fundamental high school physics concept.

Final Answer:

The relationship "Sound : Medium" is most closely mirrored by Light : Vacuum.