Reading comp PrepTest 140 · Section 4 · Question 20
Passage
Questions 20-27 . Physicists are often asked why the image of an . object, such as a chair, appears reversed
Remaining source text redacted.
Passage walkthrough
Passage SummaryTopic: Science
Paragraph 1
While the appeal of the "front-to-back" theory of how mirrors work is understandable, it ultimately fails because a correct explanation needs to include both the mirror and the person looking into it.
Key Lines:
Lines 1-4 - The question/phenomenon is brought up
Lines 4-7 - A first explanation is presented
Lines 14-16 - A second explanation is presented
Lines 21-23 - The Author points out a flaw in the second explanation
Lines 26-27 - The Author explores the appeal of the second explanation
Lines 42-44 - The Author explores another reason for the appeal of the second explanation
Lines 48-51 - The Author states her conclusion about what a proper theory of mirrors must do
Meta-Structure:
Phenomenon/Explanation (or Question/Answer, which is very similar) - Here, the phenomenon is the "reversed" image in mirrors, the question, why does that happen? One explanation is that it reverses around the human field-of-sight axis. Another is that it reverses things front-to-back, but the Author says this is "based on a false premise" (Lines 22-23). Finally, the Author concludes that a proper explanation needs to take both the observer and what mirrors do into account.
Last Thoughts:
First, this is a notoriously difficult passage, so if you struggled, you're in good company! When that happens, rely on the structure and statements of opinion. Those two things will help you get through the difficult passages.
The first paragraph is a little confusing, so we should expect some questions on that—we'll need to head back to figure out what the correct answer is for any questions dealing with the concept of field of sight axes and rotation.
One thing that's absolutely important to think about—the Author's closing statement, where we finally learn her opinion on the subject of explaining mirrors. While two theories are presented, the Author concludes not with the acceptance of one theory over the other, but rather with the adoption of a criterion by which theories should be judged. She concludes that a theory is valid "only if we consider both what mirrors do and what happens when we look into mirrors" (Lines 49-51).
How does this apply to the two theories? We know that she pointed out an appeal of the second theory (the Reverse Image theory) is that it cuts out the observer, so she believes that theory isn't a good one (which lines up with her stating it relies on a false premise). The first theory does rely on the observer to explain how a mirror works—it relies on human vision featuring a vertical axis, explaining the left-to-right reversal. But just because it matches up with a requirement for a valid theory doesn't mean the Author accepts it—she never explicitly does, so we have to be careful about selecting answers that are too accepting of that theory.
Paragraph 1
- Paragraph note
- A question/phenomenon is introduced, along with an answer/explanation
- Views, minor Meta-Structures, and the author's attitude
- Phenomenon - Mirrors reverse images left-to-right instead of top-to-bottom
- Explanation - "Field-of-Sight" explanation - the reversal reflects how human field of sight is rotated (vertical axis)
- Base example - Chair
- Paragraph note
- Another answer/explanations is presented, and the Author gives an opinion on it
- Views, minor Meta-Structures, and the author's attitude
- Explanation 2 - Mirrors reverse front-to-back, which makes sense if you think about the reflected chair as being inside the mirror
- Problem with Explanation 2 - Most notable: Based on false premise, since the "chair" inside the mirror isn't real
- Paragraph note
- Why Explanation 2 is appealing
- Views, minor Meta-Structures, and the author's attitude
- It makes sense with our senses, since we "see" the chair in the mirror and thus think of it as real
- Example - We don't focus on mirrors but on objects in them
- Paragraph note
- Another reason Explanation 2 is appealing, with the Author's rebuttal
- Views, minor Meta-Structures, and the author's attitude
- Scientists try to explain without referring to observer
- Author - When you're trying to explain an observation, you need the explanation to include the observer
While the appeal of the "front-to-back" theory of how mirrors work is understandable, it ultimately fails because a correct explanation needs to include both the mirror and the person looking into it.
Key Lines:
Lines 1-4 - The question/phenomenon is brought up
Lines 4-7 - A first explanation is presented
Lines 14-16 - A second explanation is presented
Lines 21-23 - The Author points out a flaw in the second explanation
Lines 26-27 - The Author explores the appeal of the second explanation
Lines 42-44 - The Author explores another reason for the appeal of the second explanation
Lines 48-51 - The Author states her conclusion about what a proper theory of mirrors must do
Meta-Structure:
Phenomenon/Explanation (or Question/Answer, which is very similar) - Here, the phenomenon is the "reversed" image in mirrors, the question, why does that happen? One explanation is that it reverses around the human field-of-sight axis. Another is that it reverses things front-to-back, but the Author says this is "based on a false premise" (Lines 22-23). Finally, the Author concludes that a proper explanation needs to take both the observer and what mirrors do into account.
Last Thoughts:
First, this is a notoriously difficult passage, so if you struggled, you're in good company! When that happens, rely on the structure and statements of opinion. Those two things will help you get through the difficult passages.
The first paragraph is a little confusing, so we should expect some questions on that—we'll need to head back to figure out what the correct answer is for any questions dealing with the concept of field of sight axes and rotation.
One thing that's absolutely important to think about—the Author's closing statement, where we finally learn her opinion on the subject of explaining mirrors. While two theories are presented, the Author concludes not with the acceptance of one theory over the other, but rather with the adoption of a criterion by which theories should be judged. She concludes that a theory is valid "only if we consider both what mirrors do and what happens when we look into mirrors" (Lines 49-51).
How does this apply to the two theories? We know that she pointed out an appeal of the second theory (the Reverse Image theory) is that it cuts out the observer, so she believes that theory isn't a good one (which lines up with her stating it relies on a false premise). The first theory does rely on the observer to explain how a mirror works—it relies on human vision featuring a vertical axis, explaining the left-to-right reversal. But just because it matches up with a requirement for a valid theory doesn't mean the Author accepts it—she never explicitly does, so we have to be careful about selecting answers that are too accepting of that theory.
Question prompt
The main point of
Remaining source text redacted.
Why the credited answer is right
Credited answer: A
The notes below walk through why it fits the stem and how to eliminate the rest.
Question Type
Science
Answer choices
-
Amust include two particular Remaining source text redacted.
Why choice A matches the stem
Correct. Question Type:
Main Point
Strategy Overview:
Review the main point of the passage as we stated it after reading the passage
Answer Anticipation/Relevant Lines:
This question stem gives us a bit more information than the normal Main Point question—it tells us that the main point is that "an adequate explanation of mirror images __________." In other words, what is the Author's criterion for an adequate explanation? We can answer that directly based on our anticipation, but let's walk through the normal thought process here.
The passage falls into a common pattern—the Phenomenon/Explanation (or Question/Answer) passage. When this is the case, the Author's preferred explanation is generally the main point.
Here, two explanations are given—the field-of-sight explanation (Lines 4-7), and the front-to-back explanation (Lines 14-16). While the Author is negative towards the front-to-back explanation (Lines 21-23), she never buys into the first theory, either.
Rather, as she closes out the passage, she brings up the criterion for a valid theory of mirrors—it must "consider both what mirrors do and what happens when we look into mirrors" (Lines 50-51). Since this answer asks us what the Author thinks an adequate explanation must do, let's find an answer reflecting this criterion.
Answer Explanation:
(Lines 50-51) The Author says that a valid theory of mirrors must consider what mirrors do and the observer looking into the mirror. That's two elements, so this is the correct answer.
Key Takeaway:
(D) is definitely the most tempting answer here. While the Author might have raised a debate between two sides, she clearly takes sides against one of the explanations while offering a criterion for a good explanation. When the Author takes a stand, that stand needs to be reflected in the correct answer to the Main Point question. -
Bhas yet to be Remaining source text redacted.
Why choice B is not credited
Incorrect. (Lines 50-51) The Author establishes a requirement for a valid explanation, so there has been at least some determination on what an adequate explanation would consist of. -
Cmust be determined by Remaining source text redacted.
Why choice C is not credited
Incorrect. (Lines 14-16) The Author never states that physicists should be defining this. On top of that, the argument brings up some physicists who the Author believes are wrong in defining how mirrors work! -
Dis still subject to Remaining source text redacted.
Why choice D is not credited
Incorrect. (Lines 21-23) There are two issues with this answer. First, the Author states that one of the theories rests on a "false premise (Lines 22-23), so there might not be a debate—the one theory might be generally viewed as wrong! Second, even if there are two camps of physicists who argue over these two theories, the Author's main point isn't that there is a debate—she steps back and offers an opinion on what a proper explanation must do. This is still a Main Point question, and so an answer that doesn't reflect the Author's opinion on the subject of the passage is going to be wrong! -
Eis extremely complicated
Why choice E is not credited
Incorrect. While we might think this is true based on the complexity of this passage, there's no indication that the Author thinks this material is extremely complicated.
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