1. While in the lab, you and your lab partner are using the same type of microsc

Question

1. While in the lab, you and your lab partner are using the same type of microscope with

the only difference being that you are using a source of illumination of ? = 300 nm

and your partner is using a source of illumination of ? = 425 nm.

Which of you is getting the better resolution? Explain briefly.

b. What is the theoretical resolution for your microscope if you use the 40X lens and

a wavelength of ? = 475 nm (Show calculation and report result in ?m):

c. Using the resolution value you calculated in part b, can you see objects that are

0.0002 mm apart as being distinct? Explain briefly.

d. If you are looking at a specimen with the 10X objective and your partner is

using the using the 4X objective, will there be a difference in resolution if you

are both using a source of illumination of ? = 525 nm? Explain briefly and show

calculations.

e. You are looking at a specimen under the microscope using the 4x objective lens

and have it in perfect focus but not quite centered. You want to see some more

detail in your specimen so you increase the magnification and change to the 10x

objective lens. To your surprise your specimen has disappeared! What has

happened and how can you correct it?

Explanation / Answer

1. To improve the resolution , a shorter wavelength of light is required. So, 300nm will give better resolution.

b) r = 0.61 * wavelength (lambda in nm) / Numerical aperture.

value of numerical aperture = 1

so, r =0.61 * 475 = 289.75nm ~ 0.3 mm

c) no, we will not be able to see this object.

d) no, there will be no difference because resolution depends on wavelength of light source, not on the magnification.

e) under 4x objective, the object has magnified 40 times, but under 10x objective the object has magnified 100 times. To correct this, either we have to

- switch back to 4x objective.

- move the slide in such a way that the object is visible.

- put a drop of oil on the slide

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