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

Brandon on October 28, 2018

please explain

Ans choice A (the apparent correct ans) says they are difficult to distinguish, but paragraph 2 seems to say that Physicists are confident they are picking up one and not the other. I'm not sure what i'm missing?

3 Replies

Mehran on October 31, 2018

Hi @Brandon, thanks for your post. This is indeed a very tricky question. We have to focus precisely on what is asked: what can we infer "from the description of blackbody objects" in the second paragraph? Those objects are described at lines 16-18. Let's take a close look: "commonly called 'blackbody' radiation *because experiments aimed at measuring it require objects, such as black velvet or soot, with little or no reflective capability."

Let's think about this. Why would we need objects with "little or no reflective capability" to be able to accurately measure radiation *emitted from* a so-called blackbody object? Answer choice (A) explains this: because, generally speaking, radiation reflected by and radiation emitted by an object are difficult to distinguish from one another. If that were not the case, you wouldn't need special objects to tell the difference between radiation that is emitted vs. radiation that is reflected - the two types would be distinct enough that you could just tell them apart.

Hope this helps! Please let us know if you have any additional questions.

jing jing on April 11, 2020

Why is C wrong? Thanks

Ben on April 11, 2020

Hi Jing, thanks for the question.

The idea here is that just because they found almost no ultraviolet radiation emitted from blackbody objects does not mean that "ALL" blackbody object of comparable size give off radiation at approximately the same wavelengths regardless of temperature. This is unsupported.

I hope this helps. Please let me know if you have any other questions.