Significant Figures (Fall 2011 Midterm)

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Regina Chi 2K
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Joined: Fri Sep 26, 2014 2:02 pm

Significant Figures (Fall 2011 Midterm)

Postby Regina Chi 2K » Sun Nov 09, 2014 1:41 pm

For questions such as #4 on the Fall 2011 Midterm:

"Heating Copper (I) Chloride to about 1200 C results in blue fireworks. The hot compound emits blue light with energy of 4.40 x 10^-19 J per photon. What is the wavelength of the blue light in nanometers?"

In this situation, we did not use 1200 C in our calculations to find the wavelength, but do we still consider it a part of how many significant figures our final answer has? Because although not directly involved in the equation and calculations, isn't it implied that the 1200 C has been calculated somewhere before to give us the wavelength of 4.40 x 10^-19?

Rahul Chandrupatla 3H
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Joined: Fri Sep 26, 2014 2:02 pm

Re: Significant Figures (Fall 2011 Midterm)

Postby Rahul Chandrupatla 3H » Sun Nov 09, 2014 1:49 pm

We wouldn't use the 1200C for significant figures. All that matters is the numbers we specifically are using for our calculations. Even if 1200C was used to find the energy per photon, it wouldn't matter for us because the problem gives the energy with 3 sig figs, and that's the value we use in our calculations.

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