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### Wavelength

Posted: Thu Oct 11, 2018 12:26 pm
When calculating wavelength, does it matter what the unit is? For example, the speed of light is measured in meters per second, but some wavelengths are given in terms of nanometers. Should I convert it to meters first, plug it into an equation, then re-convert it back afterwards, or does it not matter at all?

### Re: Wavelength

Posted: Thu Oct 11, 2018 12:30 pm
For equations, the units need to be the same. For your answer however I think either is fine. In lecture I remember him saying nanometers are easier to understand but it doesn't really make a difference.

### Re: Wavelength

Posted: Thu Oct 11, 2018 12:40 pm
You should convert all the units to be the same before you start the problem so you're working with the same measurements. However, I do not think it matters what units your answer is in unless the question specifically asks for it. As long as the value is the same, it should not matter if your answer is in meters or nanometers. Just be sure to convert nanometers into meters or vice versa before you start calculating so you're working with the same units throughout the problem.

Hope this helps!

### Re: Wavelength

Posted: Thu Oct 11, 2018 12:42 pm
The process by which you convert the wavelength does not really matter, but I personally find it easier to keep the wavelength units in meters (and use powers of 10) until the end; it makes it easy to track the units and make conversions involving m/s (usually the speed of light). Converting it to nm, pm, or whatever units make the type of light easily identifiable is also a personal choice. Overall, I don't think it's that important as long as you use the correct units when working through the problem or if the question asks for specific units.

### Re: Wavelength

Posted: Thu Oct 11, 2018 1:29 pm
Hi! Just make sure that when you do the conversions that all of the measurements are in the same units. If not, the answer will be wrong. In terms of the final answer, i've read to put them in meters, unless otherwise stated in the problem!

### Re: Wavelength

Posted: Thu Oct 11, 2018 1:50 pm
As the previous replies said, always keep your units consistent. A good rule of thumb is to always use SI units in your calculations (the SI unit of length is m), and then at the very end, convert to a different unit (nanometer, picometer, etc) if the question specifies so.

### Re: Wavelength

Posted: Thu Oct 11, 2018 2:27 pm
As everyone has said it is important to keep units in the calculation. It is important for the answer, but also for me personally it is easier to understand the equations used by seeing the units in the problem. SI units should be used during the calculations and then convert at the very end (if specified).

### Re: Wavelength

Posted: Thu Oct 11, 2018 6:54 pm
I think the only thing that matters is that the units are in meters, unless the question specifically states to put the answer in nanometers.

### Re: Wavelength

Posted: Thu Oct 11, 2018 7:25 pm
Units in an equation must ALWAYS be the same! You can't multiply nanometers by meters, because then what would be the units of your answer? Once you get your answer, however, it can sometimes be easier to convert to nanometers or maybe kilometers if you are giving a really large or really small number just to make sure you don't accidentally lose or gain any zeros while writing it out or using it in further calculations.

### Re: Wavelength

Posted: Thu Oct 11, 2018 8:26 pm
The answers will probably be in some form of meters, but unless the units are specified I don't think it will matter what kind of unit in meters you use. Being consistent with units is always a better choice though.

### Re: Wavelength

Posted: Thu Oct 11, 2018 9:37 pm
Since most other units that contain a measurement of length (i.e. velocity is m/s, etc.), it is best to convert measures of length into meters (m). On another note, most units are calculated using the SI units. Unless the given values and the other needed units are not in SI units, it is best to convert to SI units and then convert back to the units used in the question.