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### speed of light

Posted: Thu Oct 11, 2018 9:16 pm
When we do hw, should we use 3.0x10^8 m/s for the speed of light, or a more accurate value?

### Re: speed of light

Posted: Thu Oct 11, 2018 9:19 pm
The exact speed of light is 299,792,458 m/s, but for our purposes, 3.0x10^8 m/s is perfectly fine as well.

### Re: speed of light

Posted: Thu Oct 11, 2018 10:05 pm
In the solutions manual they recommend using 2.998x10^8 m/s for the speed of light but if you round up then yea you could use 3x10^8

### Re: speed of light

Posted: Thu Oct 11, 2018 10:38 pm
You can use 3.00 x 10^8 m/s, but you could use 2.998 x 10^8 or 2.99792 x 10^8 (in Lavelle's constants and equations sheet).

### Re: speed of light

Posted: Thu Oct 11, 2018 11:48 pm
I think in lecture he said that the speed of light in a vacuum is 3.0x10^8 m/s, but I would probably go off the "Constants and Equations" worksheet on the website.

### Re: speed of light

Posted: Fri Oct 12, 2018 12:38 am
Sort of unrelated, but since we are working solely with the speed of light in a vacuum, I'm wondering what the speed of light is when not in a vacuum (if that even makes sense?)

### Re: speed of light

Posted: Fri Oct 12, 2018 12:42 am
I don't think that it matters on the homework problems if we use 3.0 x 10^8 m/s or a more precise value, but for the tests, I would stick to using the value that is on the constants and equations sheet.

### Re: speed of light

Posted: Fri Oct 12, 2018 1:09 am
I think 3.0 x 10^8 is fine!

### Re: speed of light

Posted: Fri Oct 12, 2018 11:47 am
In response to Sam's question, the speed of light in another medium (not a vacuum) is slower than the measured value of 30 million m/s. The actual number depends on the specific medium we are talking about. For example, the speed of light in water is about 3/4 the speed of light in a vacuum.