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Comets do not give off their own light but reflect light from other so

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Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 27 Jul 2018, 09:36
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Comets do not give off their own light but reflect light from other sources, such as the Sun. Scientists estimate the mass of comets by their brightness: the greater a comet’s mass, the more light that comet will reflect. A satellite probe, however, has revealed that the material of which Halley’s comet is composed reflects 60 times less light per unit of mass than had been previously thought.

The statements above, if true, give the most support to which one of the following?


(A) Some comets are composed of material that reflects 60 times more light per unit of mass than the material of which Halley’s comet is composed.

(B) Previous estimates of the mass of Halley’s comet which were base on its brightness were too low.

(C) The total amount of light reflected from Halley’s comet is less than scientists had previously thought.

(D) The reflective properties of the material of which comets are composed vary considerably from comet to comet.

(E) Scientists need more information before they can make a good estimate of the mass of Halley’s comet.

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Re: Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 27 Jul 2018, 09:58
1+ for C
B and C are close but "too low" in B is bit extreme.


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Comets do not give off their own light but reflect light from other so  [#permalink]

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New post Updated on: 28 Jul 2018, 21:30

Conclusion

Comets don't have their own light but reflect it from other light sources. A comet's mass is estimated by its brightness. Greater the mass - more light it would reflect off of itself. New revelation by the satellite probe: Haley's comet's material is composed of material which reflects the light many times LESS per unit mass than was previously thought.
Bunuel wrote:
Comets do not give off their own light but reflect light from other sources, such as the Sun. Scientists estimate the mass of comets by their brightness: the greater a comet’s mass, the more light that comet will reflect. A satellite probe, however, has revealed that the material of which Halley’s comet is composed reflects 60 times less light per unit of mass than had been previously thought.

The statements above, if true, give the most support to which one of the following?

(A) Some comets are composed of material that reflects 60 times more light per unit of mass than the material of which Halley’s comet is composed.
Passage doesn't inform us about other comet's materials. We can not be sure of this statement just from the information provided.

(B) Previous estimates of the mass of Halley’s comet which were based on its brightness were too low.
If it takes more Halley's material to reflect the amount of light that we've seen, then Halley's must be bigger than we thought. In other words, previous estimates were too low. We have to understand the causality here: ...the greater a comet’s mass, the more light that comet will reflect...

(C) The total amount of light reflected from Halley’s comet is less than scientists had previously thought.
The point of the stimulus is not that Halley's reflects less light than we thought. Rather, it reflected a certain amount of light, which, as it turns out, requires more Halley's material to reflect. Amount of light reflected is dependent on the mass, not the other way around. The causality mentioned above is important here.

(D) The reflective properties of the material of which comets are composed vary considerably from comet to comet.
We cannot be sure of this just from the information in the passage. No information regarding this.

(E) Scientists need more information before they can make a good estimate of the mass of Halley’s comet.
Since the only factor mentioned used in estimating the mass is brightness - which is correctly known now by the satellite probe, the mass could be easily determined. No more information should be necessary to make a good estimate of the Halley's comet's mass.

Hence, the Correct Answer: (B)

EDIT: Corrected the error. I was wrong in choosing (B) over (C). Thank you Arro44 for the correct explanation. To read Arro44's detailed answer to this question click here. (Don't forget to drop a Kudos while you are there. :angel: )
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Originally posted by abhinav770 on 27 Jul 2018, 10:08.
Last edited by abhinav770 on 28 Jul 2018, 21:30, edited 1 time in total.
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Re: Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 28 Jul 2018, 01:16
How is B the official answer to this question ?

I opted for C over B for reasoning as mentioned above :?

Can anyone provide some insights on B ?
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Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 28 Jul 2018, 03:04
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C is a trap my friends.

The scientists didnt make any judgements about the amount of light reflected, but rather derived their calculations of the comets mass from their observations.

As they now found out the comments material is less reflective than though, which does not change anything about the reflection they were able to decet, it is likely that the commet is around 60 times heavier than originally anticipated.

Hope this explains why it is B.

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Re: Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 28 Jul 2018, 03:35
I still don't understand how the official answer is B.

Hi Bunuel, do you have OE for the above question? Kindly provide your inputs. Thanks !

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Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 28 Jul 2018, 03:37
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Akash720 wrote:
I still don't understand how the official answer is B.

Hi Bunuel, do you have OE for the above question? Kindly provide your inputs. Thanks !

Posted from my mobile device


OE from LSAT forum:

https://forum.powerscore.com/lsat/viewtopic.php?t=1804

Answer choice (A): Halley's is 60 times less reflective than previously thought, but that doesn't mean that there are materials exactly 60 times as reflective.

Answer choice (B): This is the correct answer choice. If it takes more Halley's material to reflect the amount of light that we've seen, then Halley's must be bigger than we thought. In other words, previous estimates were too low.

Answer choice (C): The point of the stimulus is not that Halley's reflects less light than we thought. Rather, it reflected a certain amount of light, which, as it turns out, requires more Halley's material to reflect.

Answer choice (D): There is no such comparison from comet to comet in the stimulus, so this answer choice is not supported by the author. The only referenced variation is between what we used to believe Halley's mass to be, and what recent discoveries suggest today about Halley's mass.

Answer choice (E): This stimulus presents a recent discovery that seems to provide the basis for a good estimate, so this answer choice is unsupported by the stimulus and incorrect.
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Re: Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 28 Jul 2018, 03:42
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sudarshan22 wrote:
How is B the official answer to this question ?

I opted for C over B for reasoning as mentioned above :?

Can anyone provide some insights on B ?


how it may be b is that...
think of the total light reflected as 600 units.
lets say they thought that this comet was made of material A, which has a light density of 60units/ kg
this would mean that it weighed 600/60= 10 kgs according to older calculations

now they have discovered that the actual light density is 60/60= 1unit/kg
the total light reflected still remains the same, i.e. 600 units
with the new density, the weight is now 600/1 = 600kgs according to new calculation
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Re: Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 28 Jul 2018, 03:43
Arro44 wrote:
Akash720 wrote:
I still don't understand how the official answer is B.

Hi Bunuel, do you have OE for the above question? Kindly provide your inputs. Thanks !

Posted from my mobile device


OE from LSAT forum:

https://forum.powerscore.com/lsat/viewtopic.php?t=1804

Answer choice (A): Halley's is 60 times less reflective than previously thought, but that doesn't mean that there are materials exactly 60 times as reflective.

Answer choice (B): This is the correct answer choice. If it takes more Halley's material to reflect the amount of light that we've seen, then Halley's must be bigger than we thought. In other words, previous estimates were too low.

Answer choice (C): The point of the stimulus is not that Halley's reflects less light than we thought. Rather, it reflected a certain amount of light, which, as it turns out, requires more Halley's material to reflect.

Answer choice (D): There is no such comparison from comet to comet in the stimulus, so this answer choice is not supported by the author. The only referenced variation is between what we used to believe Halley's mass to be, and what recent discoveries suggest today about Halley's mass.

Answer choice (E): This stimulus presents a recent discovery that seems to provide the basis for a good estimate, so this answer choice is unsupported by the stimulus and incorrect.


Thanks Chris !

This one was really confusing but now it's clear.
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Comets do not give off their own light but reflect light from other so  [#permalink]

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New post Updated on: 29 Jul 2018, 14:50
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rahulkashyap wrote:
sudarshan22 wrote:
How is B the official answer to this question ?

I opted for C over B for reasoning as mentioned above :?

Can anyone provide some insights on B ?


how it may be b is that...
think of the total light reflected as 600 units.
lets say they thought that this comet was made of material A, which has a light density of 60units/ kg
this would mean that it weighed 600/60= 10 kgs according to older calculations

now they have discovered that the actual light density is 60/60= 1unit/kg
the total light reflected still remains the same, i.e. 600 units
with the new density, the weight is now 600/1 = 600kgs according to new calculation


Ohh that way! Now I get it.
But, questions like these may penalize you on D-Day when you see the word "Too low" in option B and zero out the option, GMAT why you no easy? :hurt:

Thanks for the explanation rahulkashyap
What would I do without nice people like you who offers such selfless help on the forum :grin: :thumbup:
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Originally posted by sudarshan22 on 28 Jul 2018, 03:54.
Last edited by sudarshan22 on 29 Jul 2018, 14:50, edited 1 time in total.
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Comets do not give off their own light but reflect light from other so  [#permalink]

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New post 28 Jul 2018, 05:03
The key here is the wording, since you are not given a conclusion.

Comets do not give off their own light but reflect light from other sources, such as the Sun. Scientists estimate the mass of comets by their brightness: the greater a comet’s mass, the more light that comet will reflect. A satellite probe, however, has revealed that the material of which Halley’s comet is composed reflects 60 times less light per unit of mass than had been previously thought. -- The key here is that the comet is not getting darker, just a reinterpretation of mass-to-brightness ratio. In essence, the question is saying there is MORE material because it is less dense. We are not saying there is less density, which in turn would lead to brightness (and vice versa due to contrapositive relationship

To diagram: More light -- More mass
Less brightness per unit of mass -- less mass per unit than originally thought -- same amount of mass -- less dense material -- brightness unchanged


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Comets do not give off their own light but reflect light from other so &nbs [#permalink] 28 Jul 2018, 05:03
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