Q19

[kimyooji]

Q19.

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

I don't know how A could be the answer?
paragraph says physicists can monitor the radiation and tey're confident about it.

thank you!!!!

[cyruswhittaker]

Support for choice (A) is given in lines 13-22. Notice that the "major challenge" (line 13) was that the experiments require objects with little reflective capability, and in the next sentence, we learn that scientists can analyze the radiation from a blackbody object and be able to distinguish this radiation from that which is just reflected.

From this information, it is not a big leap to infer choice (A). Indeed, if (A) were not true, then it wouldn't make sense why this results in a "major challenge"

Incorrect Choices:

(B): Goes way too far.
(C): No support for this.
(D): "Any" object? No use? Goes too far.
(E): There is no support that no thermal radiation can originate from a blackbody object.

[bbirdwell]

Nice work, Cyrus! With a few edits:

Support for choice (A) is given in lines 13-22. Notice that the "major challenge" (line 13) was found by studying the radiation emitted by an object. To study that, they need to use stuff which has little or no reflective capability. Why? We can infer that it's because of (A) -- it's hard to distinguish between the emitted radiation and the reflected kind. If that weren't true, why do they need to use blackbody stuff?

Incorrect Choices:

(B): Goes way too far. Any?
(C): No support for this.
(D): "Any" object? No use? Goes too far.
(E): There is no support that no thermal radiation can originate from a blackbody object.

[wallace.rachael]

Can someone please go over this in more detail? It looks like the passage states that the physicists can be confident that they are not observing radiation reflected from the blackbody material (in lines 19-22). The answer choice seems to say that the reflected radiation and emitted radiation are difficult to distinguish from each other. When I read this answer choice, I thought it was the opposite of what the passage stated.

Can someone please clarify what I'm missing?

[noah]

Can someone please go over this in more detail? It looks like the passage states that the physicists can be confident that they are not observing radiation reflected from the blackbody material (in lines 19-22). The answer choice seems to say that the reflected radiation and emitted radiation are difficult to distinguish from each other. When I read this answer choice, I thought it was the opposite of what the passage stated.

Can someone please clarify what I'm missing?

You're on to it! Since it's generally difficult to distinguish the two types of radiation, scientists use blackbody objects, which have little or no of one of the kinds.

It'd be as if I needed to measure how loud an instrument is. You'd need to be careful that you're just measuring that instrument, not the instrument + noise from other things that might get picked up by your audio-measuring equipment. Now, imagine that some instruments tend to reflect sound, so if a noise was made near it, you'd hear it reflecting off the instrument. It'd be super difficult to measure the instrument's noise level in that case since you wouldn't know if that was noise that the instrument produced or some noise it was simply reflecting. But, if you got a blackbody instrument, one that doesn't reflect any noise, you'd have a better chance of measuring it's noise since you wouldn't have to worry about reflected noice.

(Note, that analogy is flawed in a few ways, but I hope it helps!)

Go back and re-read that second paragraph. That make sense now? If not, let's keep discussing it.

[tzyc]

I'm still confused even after reading both explanations above...and also feel A contradicts with what the sentences say, as the other poster says...

In line13-22...
the radiation emitted by an object dues to the object's temperature=blackbody radiation
Blackbod objects≠blackbody radiation (even they use blackdody for both...blackbody radiation is coming from black body objects and examples arevelet or soot...) and black body objects has little reflective capability, so they can measure how much wave only coming from black body object are...(without reflective radiation) so shouldn't the answer A say it's easy, rather than difficult if they use the black body objects? Because the physicists are confident that they are observing its thermal radiation. So the black body can shut down unnecessary radiation, isn't it??
Also, they observed less radiation than they thought, so if it's difficult to distinguish, then I think there would be more radiation.
Or is it because it requires objects to shut down reflective radiation, but it could not (not mentioned)?
Or does it mean only by using black body objects, we can measure radiation correctly...if we do not use black body objects it would be difficult? In this case, then I think the challenge is not the object's capability, but the result the psysicists have...they had results that does not follow their theory, and that was the challenge to wave theory. (so maybe a little different interpretation from what the first instructor says...or does he meant this??)

Thank you

[noah]

tz-strawberry, I think you're heading into a blackbody spiral!

Let me ask you this: Why do the scientists use the velvet or soot in these blackbody experiments?

[tzyc]

tz-strawberry, I think you're heading into a blackbody spiral!

Let me ask you this: Why do the scientists use the velvet or soot in these blackbody experiments?

Yes it's like spiral or maze...
Um, as I wrote before, I thought they used it to shut out reflected radiation...the scientists just wanted to measure the radiation that it emits...so I think the last one I wrote maybe correct:

Or does it mean only by using black body objects, we can measure radiation correctly...if we do not use black body objects it would be difficult? In this case, then I think the challenge is not the object's capability, but the result the psysicists have...they had results that does not follow their theory, and that was the challenge to wave theory. (so maybe a little different interpretation from what the first instructor says...or does he meant this??)

But then I think I was confused because what I say seems contradict with what previous poster says:

the "major challenge" (line 13) was that the experiments require objects with little reflective capability, and in the next sentence, we learn that scientists can analyze the radiation from a blackbody object and be able to distinguish this radiation from that which is just reflected.

From this information, it is not a big leap to infer choice (A). Indeed, if (A) were not true, then it wouldn't make sense why this results in a "major challenge"

I think the "major challenge" is the result itself, not "the experiments require objects with little reflective capability"...it cast doubt on scientist's theory, not the black body objects have problems (or did the previous poster say the same thing?)
So I was confused whether I interpret it correctly or not...

Could you provide additional explanation please?
Thank you

[noah]

And why are they using it to shut out reflected radiation?

Because of (A). They want to see just the emitted stuff.

Make sense now?

[tzyc]

Yes,
but...then what "major challenge" are they talking about? (the quotes I quoted last time) It seems like they have different understanding about major challenge as mine? (I thought it's the result they have, which is black body objects reflect less radiation than scientists thought)
Sorry for bothering you but really want make this clear...

Thanks!

[noah]

The major challenge is to wave theory. The blackbody is simply the experimental tools that were used (like a beaker) that helped them figure out there was an issue with wave theory and challenge it (majorly).

I disagree with Cyrus' explanation and edited Brian's to give a somewhat cleaner one.

[tzyc]

Thank you a lot Noah, I see it now