brightfield microscopy lab questions

describe the position of your hands when carrying the microscope to and from your lab bench

one hand should be under the base of the microscope to support its weight and one hand should be on the arm for balance

differentiate between the limit of resolution of the typical light microscope and that of the unaided human eye

the limit of resolution of the unaided human eye is about .2 mm. for the typical light microscope, the limit is .2 um

what two adjustments can be made to the condenser? what effect do these adjustments have on the image?

the condenser high and diaphragm can be adjusted. illumination of the specimen is increased when the condenser is raised and the diaphragm is opened

why are condenser adjustments generally preferred over the use of light intensity control?

unlike the voltage control, condenser adjustments will increase illumination without affecting the bulb life

when using the oil immersion lens what four procedures can be implemented to achieve the maximum resolution?

the maximum resolution with the oil immersion lens is achieved by using a layer of oil, using a blue filter over the light source, raising the condenser to its highest point, and opening the condenser diaphragm

why is it advisable to start first with the low power lens when viewing a slide?

the oil immersion lens has the smallest working distance and one runs the risk of striking the slide with the lens when trying to achieve focus. starting with the low power lens, which has a larger working distance, and progressing up to the oil lens is advised

why is it necessary to use oil in conjunction with the oil immersion lens and not with the other objectives?

oil is used with the oil immersion lens because the small working distance does not allow enough light to enter the lens. the oil, which has the same refractive index as glass, directs more light into the lens by limiting the loss of light

what is the relationship between the working distance of an objective lens and its magnification power?

as the power of the objective lens increases the working distance decreases

this objective lens provides the highest magnification

oil immersion

this objective lens provides the second highest magnification

high dry

this objective lens provides the lowest magnification

low power

this objective lens has the shortest working distance

oil immersion

the coarse focus knob should be adjusted only when using this objective lens

low poewr

this lens collects and focuses light from the lamp onto the specimen on the slide

condenser

this lens, aka eyepiece, often comes in pairs

ocular

diopter adjustments can be made to this lens

ocular

a diaphragm is used to regulate light passing through this lens

condenser

T/F: acetone is the safest solvent for cleaning an objective lens

false

T/F: only lint free, optically safe tissue should be used to wipe off microscope lenses

true

T/F: the total magnification capability of a light microscope is only limited by the magnifying power of the lens system

false

T/F: the coarse focus knob can be used to adjust the focus when using any of the objective lenses

false

T/F: once focus is achieved at one magnification, a higher power objective lens can be rotated into position without fear of striking the slide

true

the resolving power of a microscope is a function of:

the numerical aperture of the lens and the wavelength of light

the coarse and fine focus knobs adjust the distance between:

the stage and the objective lens

a microscope that maintains focus when the objective magnification is increased is called:

parfocal

the total magnification achieved when using a 100x oil immersion lens with a 10x binocular eyepiece is:

1000x

the most useful adjustment for increasing image contrast in low power magnification is:

closing down the diaphragm

before the oil immersion lens is rotated into place, you should:

center the object of interest in the preceding lens and place a drop of oil on the slide