### Speed of Light which is more accurate?

Posted:

**Sat Apr 21, 2018 3:34 pm**When we are calculating equations involving the speed of light, is it better to use 3.00x10^8 or 2.998x10^8? Does it really make a difference? Thanks.

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=14&t=30934

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Posted: **Sat Apr 21, 2018 3:34 pm**

When we are calculating equations involving the speed of light, is it better to use 3.00x10^8 or 2.998x10^8? Does it really make a difference? Thanks.

Posted: **Sat Apr 21, 2018 3:38 pm**

I do not believe it makes much of a difference. Someone asked this question in my discussion and my TA said that it does not matter but if we are taking a test and they give us the constant of speed on the page with all the formulas and constant, we should use whatever value they provided us, whether it be 3.0*10^8 or 2.998*10^8. This just assures us that our end results will be as accurate as the answer key.

Posted: **Sun Apr 22, 2018 11:40 am**

It does not make a big difference I know that the professor uses 3.0x10^8 while the textbook uses 2.998x10^8. If the test has the constant formula on the front page then use what they give you and if not just use one that you prefer.

Posted: **Sun Apr 22, 2018 12:48 pm**

For the speed of light I recommend using the most accurate, but rounding up to 3.00 will be fine as well as long as we use either one we are going to get an appropriate answer.

Posted: **Sun Apr 22, 2018 1:11 pm**

Technically the more accurate value for the speed of light would be 2.998x10^8. However, when it comes to constants it is always best to use the constant provided to us in either the formula sheet for the test or in the question for homework problems. As a side note, it is also best to keep your numbers as accurate on your calculator and avoid rounding until the very end, ensuring your answer will be as accurate as needed.

Posted: **Sun Apr 22, 2018 3:17 pm**

I believe that all the constants we need to know will be provided for HW, tests, etc... So I think it will be best to just use whatever is given. However, 299 792 458 m / s is more accurate.

Posted: **Sun Apr 22, 2018 6:39 pm**

in reality, the light's speed is less than 3E8. But 2.998E8 is much more complicated to calculation and maybe difficult to evaluate. Considered about above, we use 3E8 in calculation since there is not much difference. So, yes , 2.998E is actually more accurate, but not convenient for massive calculations.