I need to calculate the magnification, m of an objective lens, so I can then x it by the eyepiece value for M to get the total magnification.
I need v/u (v is dist from lens to image; u is dist of object to lens)
I'm using 1/f = 1/v+1/u rearranged for 1/v.
That's: 1/v = 1/f - 1/u. I think?
The object is 26mm away from the lens; the focal length is 25mm.
I keep getting v = 650mm
Any ideas where i'm going wrong please?
Thanks.
The procedurre you need to follow for the total magnification of a compound microscope, which is what you are talking about, is described here:
http://library.thinkquest.org/C003776/ingles/print/microscope.htm
You need to have a specified "barrel length" for the microscope (which is the separation of the lenses) in order to calculate objective magnification. The objective lens forms an intermediate image in front of the eyepiece, and the eyepiece forms an image of the intermediate image 25 cm away.
Thanks drwls, for that. However, the question acually asks me 2 things: the total M; and to find the length of the microscope! The questioner clearly thinks I have enough info to go on from what I've given above.
Charlie
To calculate the magnification of an objective lens, you need to find the distance, v, between the lens and the image and the distance, u, between the object and the lens. From there, you can use v/u to determine the magnification, m.
The formula you provided, 1/f = 1/v + 1/u, is known as the lens formula. This formula relates the focal length of a lens (f) to the distances of the object and the image from the lens. However, to calculate the magnification, we need to rearrange the formula and solve for v.
Starting with the lens formula:
1/v = 1/f - 1/u
Rearranging the equation:
1/v = (u - f)/(uf)
Now, plug in the values:
f = 25 mm
u = 26 mm
1/v = (26 - 25)/(25 * 26)
Simplifying:
1/v = 1/650
To find v, take the reciprocal of both sides:
v = 650 mm
So, your calculation of v = 650 mm is correct.
To calculate the total magnification, you need to multiply the magnification of the objective lens (m) by the magnification of the eyepiece (M). However, you haven't provided the value of m or M. Once you have these values, you can multiply them to get the total magnification.
If you have any additional questions or need further clarification, please let me know.