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Question 1
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
65%
(hard)
Question Stats:
44% (02:41) correct
56%
(02:32) wrong
based on 176
sessions
History
Date
Time
Result
Not Attempted Yet
Question 2
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
62% (01:26) correct 38%
(01:43) wrong
based on 159
sessions
History
Date
Time
Result
Not Attempted Yet
At the atomic scale, all matter exhibits properties commonly associated with both waves and particles. The classic experiment that demonstrates wavelike properties is the double-slit experiment, first performed by Thomas Young at the beginning of the 19th century. If a beam of light passes through two narrow slits and is projected onto a screen behind the slits, a pattern of light and dark fringes can be observed. The explanation for this is based on an analogy with ripples in water. If we drop two stones some distance apart, the ripples start to interfere with each other, sometimes amplifying when two crests or troughs meet, sometimes canceling when a crest meets a trough. A similar explanation holds for interference effects with visible light; the two slits act as independent sources in the same way as do the stones in water. This experiment provided convincing evidence in support of Christiaan Huygens’s wave theory of light, which eventually supplanted the older particle theory of Isaac Newton. However, in the 20th century, Einstein showed that Newton was not entirely wrong. His analysis of the photoelectric effect showed that light could behave as a particle as well as a wave. Surprisingly, electrons, which we tend to think of as particles, also demonstrate interference effects, showing that they too are waves as well as particles.
Which of the following best summarizes the findings of Young’s experiment, as described in the passage?
A The waves from independent light sources interact with one another in predictable patterns.
B Two light sources can cancel each other out, creating the observed dark fringes.
C Light exhibits properties of both particles and waves.
D Newton’s theory was permanently debunked.
E Newton’s theory was correct all along.
Based on the passage, what would we expect the light fringes in Young’s experiment to represent?
A the light particles from both slits landing on the screen
B the amplification created by the combination of both sets of waves of light
C the projection onto the screen where the light is not blocked out by the object with the slits
D the amplification created by light particles
E the projection onto the screen where the light is blocked by the object with the slits
28 Mar 2023, 05:00
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OE - Question 1
The key to this question lies in the analogy of the ripples in the water, where two troughs or crests amplify each other but one trough and one crest negate each other. Likewise, with the light waves, the two separate light sources produce waves that interact with one another and, like the crests and troughs of the water, have predictable results: the light and dark fringes. Choice (B) describes a part of Young’s findings, but you must reject it because it does not adequately describe the whole of his findings. Choice (C) cannot be the correct answer either, because the passage notes that it was not until Einstein that particle theory was returned to the theory of light. And likewise for choice (D); you are told Einstein proved that Newton’s theory was not entirely accurate and so it was not permanently debunked. Similarly, you cannot claim he was entirely correct, so (E) is out as well. This leaves choice (A), which matches your prediction.
The key to this question lies in the analogy of the ripples in the water, where two troughs or crests amplify each other but one trough and one crest negate each other. Likewise, with the light waves, the two separate light sources produce waves that interact with one another and, like the crests and troughs of the water, have predictable results: the light and dark fringes. Choice (B) describes a part of Young’s findings, but you must reject it because it does not adequately describe the whole of his findings. Choice (C) cannot be the correct answer either, because the passage notes that it was not until Einstein that particle theory was returned to the theory of light. And likewise for choice (D); you are told Einstein proved that Newton’s theory was not entirely accurate and so it was not permanently debunked. Similarly, you cannot claim he was entirely correct, so (E) is out as well. This leaves choice (A), which matches your prediction.
28 Mar 2023, 05:00
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OE - Question 2
The answer, again, comes from the ripple analogy, where two meeting crests are amplified. Thus, choice (B) is likely to be the correct answer. You can dismiss (A) since Young’s experiment is concerned solely with light as a wave, not as a particle, and answer choice (C) fails to take into account the purpose of his experiment: separating a single light source into two streams and recombining them on the screen. As for choice (D), amplification of light particles is mentioned as a possibility, but this is out of the scope of the question. Choice (E) refers to Huygens’s wave theory of light but not Young’s experiment. You have a clear answer in choice (B).
The answer, again, comes from the ripple analogy, where two meeting crests are amplified. Thus, choice (B) is likely to be the correct answer. You can dismiss (A) since Young’s experiment is concerned solely with light as a wave, not as a particle, and answer choice (C) fails to take into account the purpose of his experiment: separating a single light source into two streams and recombining them on the screen. As for choice (D), amplification of light particles is mentioned as a possibility, but this is out of the scope of the question. Choice (E) refers to Huygens’s wave theory of light but not Young’s experiment. You have a clear answer in choice (B).
