With the approach of the twentieth century, the classical wave theory

Question

With the approach of the twentieth century, the
classical wave theory of radiation—a widely accepted
theory in physics—began to encounter obstacles. This
theory held that all electromagnetic radiation—the
  (5)   entire spectrum from gamma and X rays to radio
frequencies, including heat and light—exists in the
form of waves. One fundamental assumption of wave
theory was that as the length of a wave of radiation
shortens, its energy increases smoothly—like a volume
  (10)   dial on a radio that adjusts smoothly to any setting—
and that any conceivable energy value could thus occur
in nature.

The major challenge to wave theory was the
behavior of thermal radiation, the radiation emitted by
  (15)   an object due to the object’s temperature, commonly
called “blackbody” radiation because experiments
aimed at measuring it require objects, such as black
velvet or soot, with little or no reflective capability.
Physicists can monitor the radiation coming from a
  (20)   blackbody object and be confident that they are
observing its thermal radiation and not simply reflected
radiation that has originated elsewhere. Employing the
principles of wave theory, physicists originally
predicted that blackbody objects radiated much more at
  (25)   short wavelengths, such as ultraviolet, than at long
wavelengths. However, physicists using advanced
experimental techniques near the turn of the century
did not find the predicted amount of radiation at short
wavelengths—in fact, they found almost none, a result
  (30)   that became known among wave theorists as the
“ultraviolet catastrophe.”

Max Planck, a classical physicist who had made
important contributions to wave theory, developed a
hypothesis about atomic processes taking place in a
  (35)   blackbody object that broke with wave theory and
accounted for the observed patterns of blackbody
radiation. Planck discarded the assumption of
radiation’s smooth energy continuum and took the then
bizarre position that these atomic processes could only
  (40)   involve discrete energies that jump between certain
units of value—like a volume dial that “clicks”
between incremental settings—and he thereby obtained
numbers that perfectly fit the earlier experimental
result. This directly opposed wave theory’s picture of
  (45)   atomic processes, and the physics community was at
first quite critical of Planck’s hypothesis, in part
because he presented it without physical explanation.

Soon thereafter, however, Albert Einstein and other
physicists provided theoretical justification for
  (50)   Planck’s hypothesis. They found that upon being hit
with part of the radiation spectrum, metal surfaces give
off energy at values that are discontinuous. Further,
they noted a threshold along the spectrum beyond
which no energy is emitted by the metal. Einstein
  (55)   theorized, and later found evidence to confirm, that
radiation is composed of particles, now called photons,
which can be emitted only in discrete units and at
certain wavelengths, in accordance with Planck’s
speculations. So in just a few years, what was
  (60)   considered a catastrophe generated a new vision in
physics that led to theories still in place today.    1 
 1. Which one of the following most accurately states the main point of the passage?

(A) If classical wave theorists had never focused on blackbody radiation, Planck’s insights would not have developed and the stage would not have been set for Einstein.
(B) Classical wave theory, an incorrect formulation of the nature of radiation, was corrected by Planck and other physicists after Planck performed experiments that demonstrated that radiation exists as particles.
(C) Planck’s new model of radiation, though numerically consistent with observed data, was slow to win the support of the scientific community, which was critical of his ideas.
(D) Prompted by new experimental findings, Planck discarded an assumption of classical wave theory and proposed a picture of radiation that matched experimental results and was further supported by theoretical justification.
(E) At the turn of the century, Planck and Einstein revolutionized studies in radiation by modifying classical wave theory in response to experimental results that suggested the energy of radiation is less at short wavelengths than at long ones.

2 
 2. Which one of the following does the author use to illustrate the difference between continuous energies and discrete energies?

(A) radio waves
(B) black velvet or soot
(C) microscopic particles
(D) metal surfaces
(E) radio volume dials

3 
 3. Which one of the following can most clearly be inferred from the description of blackbody objects in the second paragraph?

(A) Radiation reflected by and radiation emitted by an object are difficult to distinguish from one another.
(B) Any object in a dark room is a nearly ideal blackbody object.
(C) All blackbody objects of comparable size give off radiation at approximately the same wavelengths regardless of the objects’ temperatures.
(D) Any blackbody object whose temperature is difficult to manipulate would be of little use in an experiment.
(E) Thermal radiation cannot originate from a blackbody object.

4 
 4. The author’s attitude toward Planck’s development of a new hypothesis about atomic processes can most aptly be described as

(A) strong admiration for the intuitive leap that led to a restored confidence in wave theory’s picture of atomic processes
(B) mild surprise at the bizarre position Planck took regarding atomic processes
(C) reasoned skepticism of Planck’s lack of scientific justification for his hypothesis
(D) legitimate concern that the hypothesis would have been abandoned without the further studies of Einstein and others
(E) scholarly interest in a step that led to a more accurate picture of atomic processes

5 
 5. The passage provides information that answers each of the following questions EXCEPT:

(A) What did Planck’s hypothesis about atomic processes try to account for?
(B) What led to the scientific community’s acceptance of Planck’s ideas?
(C) Roughly when did the blackbody radiation experiments take place?
(D) What contributions did Planck make to classical wave theory?
(E) What type of experiment led Einstein to formulate a theory regarding the composition of radiation?

6 
 6. The primary function of the first two paragraphs of the passage is to

(A) describe the process by which one theory’s assumption was dismantled by a competing theory
(B) introduce a central assumption of a scientific theory and the experimental evidence that led to the overthrowing of that theory
(C) explain two competing theories that are based on the same experimental evidence
(D) describe the process of retesting a theory in light of ambiguous experimental results
(E) provide the basis for an argument intended to dismiss a new theory

7 
 7. The passage is primarily concerned with

(A) discussing the value of speculation in a scientific discipline
(B) summarizing the reasons for the rejection of an established theory by the scientific community
(C) describing the role that experimental research plays in a scientific discipline
(D) examining a critical stage in the evolution of theories concerning the nature of a physical phenomenon
(E) comparing the various assumptions that lie at the foundation of a scientific discipline

HASTOWINGMAT · Answer

Sajjad1994

Can you please post the answer for Q7. I was confused between option D and E.

Sajjad1994 · Answer

(D)  is the winner, acknowledging that two theories are part and parcel of the text and choosing the apt phrase  “critical stage”  to describe Planck’s revolutionary achievement.

(E)  is doubly off. The only  “assumption”  that plays a major role is the one  (line 7+)  that underlay classical wave theory, and the passage deals not with “a scientific discipline” per se but rather, to use correct choice (D)’s superior phrase, with  “a physical phenomenon.”

Answer: D

tkorzhan1995 · Answer

Sajjad1994 , can you please explain why the correct answer for #2 is E and not A? Is E correct because of the following information in par 1? 
 One fundamental assumption of wave
theory was that as the length of a wave of radiation
shortens, its energy increases smoothly—like a volume
(10) dial on a radio that adjusts smoothly to any setting

tkorzhan1995 · Answer

Sajjad1994 , GMATNinja, for Q7, could you please help to identify what critical stage in the evolution of theories has been discussed in the passage? What paragraph i should be referring to determine this information?

2.Why C is not correct? Determined that passage is emphasizing the importance of Planck's research because it generated a new vision in physics that led to theories that are still in place today

Sajjad1994 · Answer

Hello tkorzhan1995

Lines 9–10 vs. lines 40–42:  two visions of wave theory illustrated by the image of a radio dial.

(A) —The question is, how do waves behave? In which of the two types of energies? So the waves aren’t used to illustrate those energies. So  A  is not correct.

Sajjad1994 · Answer

Experimental research doesn’t come in but twice—in  lines 26–31 , and  paragraph 4.  There’s a lot of additional discussion that  (C)  doesn’t encompass.

PS: I will post the passage summary and map within a few minutes.

Sajjad1994 · Answer

Passage summary and Map

We learn quickly that the Topic is wave theory, and that the Scope will be  “obstacles”  to wave theory.  Paragraph 1  explains what wave theory is, since the testmakers know that most of us do not have a physics background. The key concept to take away is the idea that in the classical model, a wave’s radiation is supposed to increase smoothly (like a radio dial’s smoothly increasing volume) as the wave length gets shorter—a concept that all of us can visualize readily.

Paragraph 2  explains that thermal or  “blackbody”  radiation didn’t follow the expected classical pattern, and the prediction as explained in  lines 22–26  is exactly what we heard about at  lines 7–9 . But the prediction was foiled: instead of increased radiation at shorter wavelengths, researchers were chagrined to find none.

In  paragraph 3 , we are presented with Max Planck, who rejected the smoothly-increasing-energy model in favor of a discrete/”jump from click to click” model that got the calculations right but that met with opposition because of a lack of evidence.

Paragraph 4  vindicates Planck, with no less a heavy hitter than Einstein providing evidence, some theoretical and some empirical, that the discontinuous-energy hypothesis was right all along. The overall Purpose is revealed as an effort to explain how Planck revolutionized wave theory. Your

Roadmap might look like this:

Paragraph 1 —Classical model: smooth, continuous waves

Paragraph 2 —Blackbody (thermal) radiation doesn’t fit

Paragraph 3 —Planck’s discrete model

Paragraph 4 —Evidence for same provided; Planck was right

Sajjad1994 · Answer

Explanation

1. Which one of the following most accurately states the main point of the passage?

Difficulty Level:   650-700

Explanation

Correct  choice (D)  manages to bring in the essence of every paragraph: classical wave theory (Paragraph 1), the findings that cast doubt on it (Paragraph 2), Planck’s model (Paragraph 3), and the later support for Planck (Paragraph 4).

(A)  is wholly hypothetical—” if such and such, then such and such wouldn’t have happened”; but the passage is all about what did happen.

(B)  misunderstands the shift from the classical model to Planck’s hypothesis as a “correction,” when what Planck (whom (B) improperly robs of sole credit) came up with was a wholly different way of looking at the matter of wave energy. Moreover, Planck wasn’t an experimenter but rather a theoretician, at least as far as the passage tells us.

(C)  focuses solely on  lines 43–47 , far too limited a scope for a Global right answer.

(E)  wrongly gives Planck and Einstein co-credit (in the passage, the former had the notion and the latter supported it), and wrongly suggests that the problem with lines 7–9 is that longer wavelengths actually carry greater energy when the problem was simply that a key kind of radiation failed to conform to the classical model.

Answer: D

Sajjad1994 · Answer

Explanation

7. The passage is primarily concerned with

Difficulty Level:   700

Explanation

All of the choices are pretty abstract in nature, so if you’re unable to predict the answer that may be understandable. The important thing is to analyze the choices in terms of the Topic, Scope, and Purpose as you’ve identified them heretofore.

(A) —Since Planck’s theory was ultimately vindicated by experiments rather than mere speculation, (A)’s primary focus is way off.

(B)  may be a bit tricky. The overall passage details how a new theory became established; why the old one (the classical model) was seen as falling short is pretty much polished off in  lines 26–31 .
 
 (C) —Experimental research doesn’t come in but twice—in  lines 26–31 , and  paragraph 4 . There’s a lot of additional discussion that  (C)  doesn’t encompass.

(D)  is the winner, acknowledging that two theories are part and parcel of the text and choosing the apt phrase  “critical stage”  to describe Planck’s revolutionary achievement.

(E)  is doubly off. The only “assumption” that plays a major role is the one (line 7+) that underlay classical wave theory, and the passage deals not with  “a scientific discipline”  per se but rather, to use correct choice (D)’s superior phrase, with  “a physical phenomenon.”

Answer: D

Sajjad1994 · Answer

Explanation

4. The author’s attitude toward Planck’s development of a new hypothesis about atomic processes can most aptly be described as

Explanation

The author clearly admires Planck for his contribution to physics, and of the five  choices (E)  best reflects that admiration. Yes,  “scholarly interest”  sounds rather neutral and clinical, but look at the writing. Neutral and clinical seems about right.

(A)  is half-right (in its admiration for Planck’s intuitive leap) and half-wrong (in its suggestion that Planck reinforced, rather than supplanted, classical wave theory).

(B)  neglects to note that Planck held a position that was  “then bizarre” (lines 38–39) . In any case it would be odd for our author to evidence surprise, mild or otherwise, for events that occurred around 1900.

(C)  reflects the likely view of classical physicists back when Planck came up with his idea, cf.  lines 44–47.

(D) —That Einstein & co. came to the rescue doesn’t make it certain that Planck’s hypothesis would have been abandoned, by Planck or by anyone else, in their absence. This is one of those hypotheticals that the author is wise to avoid altogether.

Answer: E

gullyboy09 · Answer

(D) examining a critical stage in the evolution of theories concerning the nature of a physical phenomenon

In this option of question 7, not sure we can use "theories" here. It was just a wave theory whose evolution is discussed at length (Experiment failure -> Plank Hypothesis -> Einstien's explanation).

gullyboy09 · Answer

1. Which one of the following most accurately states the main point of the passage?

D) Prompted by new experimental findings, Planck discarded an assumption of classical wave theory and proposed a picture of radiation that matched experimental results and was further supported by theoretical justification.

Can someone point me where it is referred that Planck was prompted by new experimental findings. Yes he was a wave theorist, but "prompted by" seems to me a jump. I chose D as best of all but not convinced.

egmat · Answer

Hi gullyboy09,

Good instinct to test whether "prompted by" is actually earned, since that's exactly how a main-idea trap sneaks past you. Here the phrase  is  supported, and the support sits in paragraph  3 .

Look at the sequence the passage lays out:

Paragraph 2  gives us the experiments first: "physicists using advanced experimental techniques  near the turn of the century " found almost no radiation at short wavelengths - the "ultraviolet catastrophe," explicitly "the major challenge to wave theory."

Paragraph 3  then introduces Planck, whose hypothesis " accounted for the observed patterns  of blackbody radiation" and "thereby obtained numbers that perfectly fit the  earlier  experimental result" (lines  42 - 44 ).

That word  "earlier"  is the key. It tells you the experiments came  before  Planck's move, and that his whole aim was to produce numbers matching them. A hypothesis built to fit results that already existed is, in plain terms, a hypothesis  prompted by  those results. The passage doesn't need the literal words "prompted by" - the ordering plus "accounted for" and "earlier experimental result" give you the causal link cleanly.

So you're not adding an outside assumption; you're reading the timeline the author actually spells out.

A quick way to feel why this counts as support:  imagine a sentence like  "The bridge kept collapsing. Then an engineer designed a new support that fit exactly what the collapse data showed."  You'd say the new design was  prompted by  the collapses - even though the sentence never uses that phrase. The "earlier data it fit" tells you the design was a response to it. Planck's case reads the same way.

That's the only place "prompted by" needed backing, and it holds - so  D  is safe.

Answer: D

gullyboy09 · Answer

Hey, thanks for all your help. Just because something has happened before he proposed his hypothesis doesn't guarantee it prompted him. It's supported, but cannot be inferred, and to use that in "Main point" of the passage is far fetched IMO.

With the approach of the twentieth century, the classical wave theory

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With the approach of the twentieth century, the classical wave theory

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