Ch 22-3 Quiz

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A person has a farpoint of 1.944 m. What is the focal length of the corrective lens which shifts the farpoint to infinity (sheet 25,28) ? Indicate with a positive(negative) sign whether the lens is converging (diverging), i.e. the person is far-(near-)sighted

The answer is equal to the farpoint value, in this case 1.944m. Answer is negative because the lens is diverging

The eyepiece lens of a microscope has a focal length of 4.059 cm. The distance between the objective lens and eyepiece lens is 17.34 cm. What is the magnitude of the overall magnification of the microscope if the objective lens has a focal length of 7.769 mm (sheet 30,31) ? Indicate with a positive (negative) sign whether the image made by the microscope is upright (inverted).

F_e = 4.059 cm
F_o = 7.769mm = .7769 cm
L= 17.34 cm

Use the equation M = -(25cm)*L / (F_e*F_o)
Plug everything in and that should work. You can stay in cm for the equation, just make sure you convert the focal length of the objective lens from mm to cm, because you at least want everything to be uniform.
Answer is negative .

The objective lens of a telescope has a focal length of 0.628 m. What is the overall angular magnification of the telescope if the focal length of the eyepiece is 9.751 cm (sheet 34) ? Indicate with a negative (positive) sign whether the final image is virtual and inverted (real and upright) relative to the object.

F_o = .628 m
F_e = 9.751 cm = .09751 m

M = -(F_o/F_e)
Plug everything in, making sure everything is in consistent units
Answer is negative

Still working on question 2, can't seem to figure it out just yet..

1/f=(1/.25)-(1/# given in m)

answer is positive

still having a prob with # 2
i tried the solution as shown on the cd as well as the one posted above....i still cant seem to get a proper answer for this......anyone have any hints? am i forgetting something?

for question number 2 use the formula that guest385 posted it works!

BTW the power (in diopters)=1/f

btw the formula given is correct, just follow the right side of the equation and that's just the answer

1/.25 - 1/given number

[positive]