SAT OwlQuestion bank / Rhetorical Synthesis
While researching a topic, a student has taken the following notes:
• Refracting telescopes use lenses to gather and focus light.
• Reflecting telescopes use curved mirrors to gather and focus light.
• A large lens can sag under its own weight because it can be supported only at its edges.
• A mirror can be supported across its entire back, so mirrors can be made much larger.
• The largest refracting telescope ever used for research, at Yerkes Observatory, has a lens about 40 inches across.
The student wants to explain why reflecting telescopes can be built larger than refracting telescopes. Which choice most effectively uses relevant information from the notes to accomplish this goal?
Because mirrors, unlike lenses, can be supported from behind rather than only at their edges, reflecting telescopes can be made much larger than refracting telescopes.
Refracting telescopes use lenses, while reflecting telescopes use curved mirrors to gather and focus light.
The largest refracting telescope, at Yerkes Observatory, has a lens about 40 inches across, though lenses can sag under their own weight.
Both refracting and reflecting telescopes gather and focus light, but they do so with different components.
Show answer and explanation
Answer: A
The goal asks for a reason, so look for a choice that explains cause and effect. Choice A gives the cause (mirrors can be supported from behind, lenses only at their edges) and the result (reflecting telescopes can be much larger). Choices B and D only describe how the two telescopes differ, and choice C mentions sagging lenses without ever comparing them to mirrors.
Choice B states the basic difference between the two telescopes but never explains why that difference allows reflectors to be larger.
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