So here it says in UV Vis Spectroscopy, the absorbance represents the quantity of light that a sample absorbs, while the percent transmittance represents the amount of light that passes through a sample. Calculate the percent transmittance of a substance if its absorbance is measured as 0.419. What we need to realize here is that absorbance and percent transmittance are basically opposites of one another. If you are absorbing 100% of the light by the substance, that means there is 0% transmittance going on. And conversely, if you are transmitting 100%, that means that 0% of light is being absorbed.
So they kind of work against each other. Here, we're going to say that percent transmittance, so percent t equals your anti-log to the minus absorbance. That's the formula we use to determine what our transmittance will be. Then what we're going to say here is we're going to calculate 10-0.419. So that's going to equal here 101.581.
So then when we punch that in, we're going to get here 38.1%. So that represents 38.1% of light passing through the sample, which means that the remainder of 100% is being absorbed by that sample. So you'd say absorbance would be just 100% minus that number. So remember, they're opposites of one another.
If one is doing its job 100%, the other one would be 0 percent. And you've got to find a way of balancing the two in terms of your sample itself. The more concentrated your sample becomes, the harder it is for the light to pass through it. So the more it'll absorb light. Since we've done that one, let's move on to the next question here.
We say if your percent transmittance is 39.1%, determine the absorbance. Pretty straightforward. We're going the opposite way. See if you can manipulate this equation to get the desired equation to figure out true absorbance.
