26) For this question, we are trying to find the intensity of a laser beam. We can write out the general form for the intensity of light.
It is a good idea to quickly use dimensional analysis to check that we are on the right track. Looking at the answer choices, we see they all have units of W/m^2.
We are directly given the power, so as long as we convert it from mW to W, we can directly plug this in. Next, we need to figure out the area. If we think about this logically, the laser beam will be shot out in a circular area. So we can use the given radius to find the area of a circle.
Note that although this isn't an answer choice, the test producers state that choice D had a typo and should be the correct answer.
Answer: D
留言