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Comets do not give off their own light but reflect light

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CEO
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Comets do not give off their own light but reflect light [#permalink]

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New post 10 Mar 2004, 21:09
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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 by their brightness: the greater a comets 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 Halleys comet which were base on its brightness were too low.

(C) The total amount of light reflected from Halleys 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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New post 10 Mar 2004, 21:15
B.

A - talks about difference in material
C - reverse of whatever the paragraph talks about
D - this talks about preperties of reflective material
E - May be true but not the relevant answer
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Re: [#3] CR Challenge : Halleys' Comet [#permalink]

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New post 10 Mar 2004, 22:47
praetorian123 wrote:
Rules
1. Time yourself
2. Solve this seperately.The correct and fastest solution wins
3. After you have reached your answer, explain your solution clearly, and write down your times. if you dont want to be specific, please write down: <2min or >2 min

Use all the concentration ability you can. Good Luck.


16. 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 by their brightness: the greater a comets 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 Halleys comet which were base on its brightness were too low.

(C) The total amount of light reflected from Halleys 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.


KPADMA and Geethu, I vouch "B" should be wrong.
If we see to argument stem closely, it reads
" Scientists estimate the mass of comets by their brightness " and
"the material of which Halley's comet is composed reflects 60 times less light per unit of mass than had been previously thought."

gives that previous light received from Halley's comet was exaggerated incredibly.

Now, the stem sentence "the greater a comets mass, the more light that comet will reflect" will drive us to conclusion that it was previously exaggeration of mass and lowering of mass.

Whats say, KPADMA and Geethu ?

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New post 10 Mar 2004, 23:03
Quote:
16. 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 by their brightness: the greater a comets 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 Halleys comet which were base on its brightness were too low.

(C) The total amount of light reflected from Halleys 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.


Buddies, i will go for "C" here, "C" can be most inferrable then any other choices.

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Re: [#3] CR Challenge : Halleys' Comet [#permalink]

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New post 11 Mar 2004, 03:14
Dharmin wrote:
KPADMA and Geethu, I vouch "B" should be wrong.


Dude...

I too think B is the wrong answer!

Hence in the available options, I too feel, C is the most appropriate conclusion.

(Actually the most appropriate conclusion, if available, would have been the opposite of B ie

"Previous estimates of the mass of Halleys comet which were base on its brightness were too *high*"

OR

in other words B would have been the right conclusion if the last line of the para read

"A satellite probe, however, has revealed that the material of which Halley's comet is composed reflects 60 times *more* light per unit of mass than had been previously thought.")
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New post 11 Mar 2004, 04:18
Another vote for B...

and here's my explanation.

A, D and E are far out.

It's between B and C.

We can rule out C because we know that the amount of total reflected light as received by the scientists has not changed, rather it's the light reflected per unit mass and the estimated mass of the comet based on this that have changed. Which leaves us with the correct answer B.

Additionally, we can verify B mathematically...

Suppose the light reflected per unit mass earlier was l1 and the recent value is l2. Lets assume the estimated masses of the comet based on these values are M1 and M2, respectively...

total light reflected by the comet
L = l1 x M1 = l2 x M2

given that l1 = 60 x l2

therefore M1 = M2 / 60

whic means the estimated mass based on the previous value was low!!!!
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Re: [#3] CR Challenge : Halleys' Comet [#permalink]

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New post 11 Mar 2004, 06:16
very impressive, guys. :)

B is the correct answer.

Do i need to explain?? let me know.

pusht , great work.
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Re: Comets do not give off their own light but reflect light [#permalink]

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New post 15 Apr 2016, 03:33
The official answer is B? I don't understand why?
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Re: Comets do not give off their own light but reflect light [#permalink]

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New post 16 Apr 2016, 03:48
james33 wrote:
The official answer is B? I don't understand why?

Hi james33 !
Let me try to explain
First, the question

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 by their brightness: the greater a comets 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 Halleys comet which were base on its brightness were too low.

(C) The total amount of light reflected from Halleys 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.

Now, lets look at it both mathematically and verbally,

Mathematical situation: Brightness is directly proportional to Mass of the comet.

The passage only talks about the material of the haley's comet. We do not really know anything about the other comets. Considering this point --> A and D are out

The scientists now know for sure that the material of haley's comet reflects 60 times less light than it actually should. So now when the scientists know about this, do they need more information to calculate the mass of haley's comet? We cant really say can we? Thus, E is also out.

Consider Option C
The total amount of light reflected from Halleys comet is less than scientists had previously thought. This is simply irrelevant, the amount of light reflected from the comet has not changed, its the same as it was observed, the scientists just got to know that the light that was reflected was less accroding to its mass. So C is also out.

As stated earlier, Mass of a comet is directly proportional to Brightness it reflects,but haley's comet was not reflecting the light it should be actually reflecting(mathematically, the constant or direct proportionality that is used in the mass calculation formula does not hold good with haley's comet). Thus, the mass calculated will be much lower than the original formula gave us. B is your answer.

Hope it helped. :)
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Re: Comets do not give off their own light but reflect light   [#permalink] 16 Apr 2016, 03:48
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