Calculating the Angle Subtended by Red Blood Cells Under a Microscope

[gadawg90]

A typical red blood cell subtends an angle of only 1.90E-5 rad when viewed at a person's near-point distance of 25.0 cm. Suppose a red blood cell is examined with a compound microscope in which the objective and eyepiece are separated by a distance of 12.5 cm. Given that the focal length of the eyepiece is 2.56 cm, and the focal length of the objective is 0.500 cm, calculate the magnitude of the angle subtended by the red blood cell when viewed through this microscope.


1/f=1/di+1/do

i don't really know how to start this problem. help would be appreciated.

 

[jbsteele]

Let's start by rearranging the equation to solve for di: di = f*(1/do - 1/f)Now, let's substitute the given values into di:di = 2.56 cm * (1/0.500 cm - 1/2.56 cm)di = 21.14 cmNow we can use the angle formula:angle = 2*arctan(object size/2*distance)angle = 2*arctan(1.90E-5 rad/(2 * 21.14 cm))angle = 8.41E-6 rad