Page 1 of 1

### Speed of Light Constant

Posted: Thu Oct 12, 2017 11:23 pm
For the problems given in the book, the textbook uses the constant c= 2.998 x 10^8 m/s, while the module examples use 3.00 x 10^8 m/s. For the problems assigned, should we use what is given in the textbook, or what is used in the module?

### Re: Speed of Light Constant

Posted: Thu Oct 12, 2017 11:41 pm
I would use 2.998x10^8 to be more accurate but when you round it probably won't make a big difference. Also on the test I'm sure they'll give us the constants they'd want us to use.

### Re: Speed of Light Constant

Posted: Thu Oct 12, 2017 11:48 pm
I would use 3.00 x 10^8 for the homework problems, since Dr.Lavelle used it in his lecture~ but like the above reply said, i'm sure it will be more clear on the tests

### Re: Speed of Light Constant

Posted: Fri Oct 13, 2017 1:12 am
Professor Lavelle told my TA that we would be given constants on the tests. He didn't specify which ones, so I assume the speed of light will be there as well. However, just in case, this may be a good one to have memorized, since it's pretty simple.

### Re: Speed of Light Constant

Posted: Fri Oct 13, 2017 10:23 am
Would this also apply to Planck's constant? Sometimes I see 6.626*10^-34 Js but other times it's shortened to 6.63*10^-34 Js.

### Re: Speed of Light Constant

Posted: Fri Oct 13, 2017 10:37 am
Would this also apply to Planck's constant? Sometimes I see 6.626*10^-34 Js but other times it's shortened to 6.63*10^-34 Js.
I would use 6.626*10^-34 Js, my TA said to use that and in general, it is just more accurate. When it comes to the test I think Planck's constant should be given on our sheet, and if it is, always use whatever the sheet says because it is probably safest to be as close as possible to how the TA or teacher who is grading it will be doing it.

### Re: Speed of Light Constant

Posted: Fri Oct 13, 2017 11:12 am
When it comes to constants, use the sig figs that are given in the problem to determine how many values past the decimal point to us in the speed of light constant or plank's constant.

### Re: Speed of Light Constant

Posted: Fri Oct 13, 2017 11:43 am
Honestly, it doesn't really matter. You will get the correct answer either way. But it would be safer to be more exact so I would suggest using 2.998*10^8. Just remember to round to the nearest Sig Fig.

### Re: Speed of Light Constant

Posted: Fri Oct 13, 2017 2:56 pm
I would use 2.998*10^8 due to it being the one used in the textbook. Stay with the most accurate number.

### Re: Speed of Light Constant

Posted: Fri Oct 13, 2017 4:00 pm
Using 2.998 x 10^8 is definitely the more accurate number. However rounding it to 3 won't cause too much of an error bound, so I don't think you would get the question wrong. But 2.998 is definitely the safe option because it is more accurate.

### Re: Speed of Light Constant

Posted: Sat Oct 14, 2017 1:11 pm
Using either 3 or 2.998 on the homework doesn't really matter, just make sure you use the one that the constant sheet uses for the test.

### Re: Speed of Light Constant

Posted: Sun Oct 15, 2017 12:52 pm
I would use 2.9988x10^8 just because it is more accurate; however, if 3.00x10^8 was the number given in the problem then I would use that one instead.

### I don't know how to post my own topic

Posted: Sun Oct 15, 2017 1:02 pm
Can someone please explain how to start a new topic on this please? I also don't understand 30 C on the post module for Photoelectric effect

### Re: Speed of Light Constant

Posted: Sun Oct 15, 2017 7:33 pm
I have been using 3.00 for the most part and it hasn't caused any error. All of my answers have been accurate and as long as you show your work on the tests/quizzes, you shouldn't lose any points for using one versus the other.

### Re: Speed of Light Constant

Posted: Sun Oct 15, 2017 9:55 pm
Since 3.00 x 10^8 m/s is the constant that Dr. Lavelle uses in lecture, I think it is safe to use that on our homework and on tests since the TAs grade them and they know what Lavelle has taught us (i.e 3.00 x 10^8 m/s).

### Re: I don't know how to post my own topic

Posted: Sun Oct 15, 2017 9:56 pm
Kayla Ikemiya 1H wrote:Can someone please explain how to start a new topic on this please? I also don't understand 30 C on the post module for Photoelectric effect
you have to go to board index --> chem 14a --> select which topic your question pertains to and then click post a new topic

### Re: Speed of Light Constant

Posted: Sun Oct 15, 2017 9:58 pm
2.998 x 10^8 m/s is more accurate, but Professor Lavelle uses 3.00 x 10^8 in his lecture slides and example problems, so I don't think using 3.00 x 10^8 would be an issue.

### Re: Speed of Light Constant

Posted: Sun Oct 15, 2017 10:40 pm
I think any of these two values will be okay. Using 3.00*10^8 will only give you easier values to work with.

### Re: Speed of Light Constant

Posted: Sun Oct 15, 2017 11:04 pm
Any would be fine since they are relatively close enough, but I usually would use 3.00x10^8 m/s.