Ex 1:Brightfield Compound Microscope

Question 0

Objective lens

Answer 0

Produces a magnified image as light bends and passes from specimen to this part of the microscope

Question 1

What are the condenser lens?

Answer 1

Allows for uniform illumination of specimen by concentrating the light that passes through it

Question 2

Why does a specimen appear dark against a dark background?

Answer 2

Light is transmitted through a specimen; specimen restricts light

Question 3

What is total magnification?

Answer 3

Ocular magnification times Objective magnification

Question 4

What is resolution?

Answer 4

The clarity of an image

Question 5

What is resolving power?

Answer 5

Minimum distance that two points can be separated and still distinguish as separate points

Question 6

What is resolving power dependant on?

Answer 6

The amount of light gathered by lens. As light leaves slide contain specimen, it refracts away from the lens resulting in lost light rays

Question 7

Why is immersion oil used?

Answer 7

Fluid has same refractive index as glass. Light leaving glass will not bend as it enters oil and more light will be collected into objective lens, increasing resolution

Question 8

What is numerical aperture

Answer 8

Measure of a len’s ability to capture light from the specimen and use it to make an image

Question 9

What factors does numerical aperture depend on?

Answer 9

Size of the cone of light the lens can receive. And the medium between the lens and specimen (air or oil)

Question 10

What is the formula for resolving power?

Answer 10

RP= (0.61)(lamda wavelength)
—————
NA

Question 11

Is a higher numerical aperture better?

Answer 11

Yes, the higher the NA the better the resolving power. The resolving power distance will be smaller

Question 12

Why do microscopes employ blue light? How does this alter RP?

Answer 12

Blue light has a wavelength of 475nm. Better resolving power because compared to red light the numerator from the RP formula will be smaller. RP will be a smaller distances meaning a better resolution

Question 13

What is working distance?

Answer 13

Distance between specimen and objective lens. Increase magnification means decreasing working distance

Question 14

What is the microscopic field/field of view?

Answer 14

Area of slide you see when looking through the lens. As magnification increase size of microscopic field decreases

Question 15

What is parfocal?

Answer 15

The lens allow specimen to remain almost in focus after rotating to a different objective lens. Only fine focus knob is needed after rotation to higher objective magnification

Question 16

What is interpupillary distance adjustment?

Answer 16

Perfect bio ocular vision. Obtained by sliding ocular lens until you see one circle of light when looking through both eyepieces

Question 17

What is Koehler Illumination

Answer 17

Aligning and adjusting field iris diaphragm will focus light on specimen. Also reduces stray light which can affect image definition and contrast, and evenly illuminates field of view to minimize heating of specimen

Question 18

Name the four adjustments that can improve image

Answer 18

1 Condenser height
2 Field Iris diaphragm
3 Aperture iris diaphragm
4 Light intensity