- Messages
- 179
- Reaction score
- 161
- Points
- 53
Here you go for the 2016 one.
You can begin by looking at the thick line at the left and then the middle one. From the thick to the middle it's one stage micrometer division. Now see if it coincides perfectly with any line on the EPG. Luckily, both lines do. The first thick line coincides at the 10 EPG mark, and the middle line coincides with the 50 EPG mark. Thus, 50 - 10 = 40 EPG units are equal to 1 stage micrometer division, and 1 stage micrometer division is 0.1 mm, so 40 EPG units are equal to 0.1 mm. Thus, 0.1/40 = 1 EPG unit is 0.0025 mm.
Knowing that, the next step is finding the area. For the area you need the radius. You can't do that with a stage micrometer (or else we wouldn't have needed an EPG in the first place) because not only is it not precise enough due to being magnified so much, it's also not in the center, and the radius is always from the edge to the center. The EPG however is. So your next step is to get the radius in terms of EPG units. Rather than estimating radius, it's better to get diameter then divide it by 2. The diameter starts at 0 and if you look closely goes all the way to 100. You can't read "100" written but if you count from 95 upwards you'll see that it's exactly 5 more divisions, so this means that the diameter is perfectly equal to 100 EPG divisions. The radius then is 100/2 = 50 EPG divisions.
1 EPG division was 0.0025 mm, so 50 EPG divisions = 0.0025 x 50 = 0.125 mm = the radius of the field of view. Answers seem to be in micrometers so let's convert this to micrometers beforehand. 0.125 x 1000 = 125 micrometers. The radius is 125 micrometers. Now it's very easy. Area is pi tiimes r squared or pi times r times r. In the format of the answers they've given us, it should be pi x 125 x 125, which is option C.
