MIMG 105 Midterm Exam Questions &
Answers (Grade A+)
Sensitivity -
correct answer ✅Actually being able to see your object (if it's in
the field of view)
Specificity -
correct answer ✅Being able to identify certain objects in the
image. Commonly present in LM with fluorescence microscopy and
in TEM obtaining specificity is only possible with immunogold
particles that are specific to the antigens of interest. Can use
polyclonal or monoclonal.
Contrast -
correct answer ✅Being able to distinguish an object from its
background
Resolution -
correct answer ✅The minimum distance required to differentiate
between objects. Higher resolution means smaller numbers in nm.
What are the key properties of a microscope? -
correct answer ✅Wave: Must determine what particles to use to
determine wavelength and eventually the resolution of the final
image. Photons of visible light (400-700nm) >neutrons
,MIMG 105 Midterm Exam Questions &
Answers (Grade A+)
Lens: one would need a lens with a suitable numerical aperture to
let a beam of light or electrons through and to bend the waves for it
to converge onto a focal point. The lens has a specific focal length
(it's different for every lens). Magnification: producing an enlarged
image
Brightfield Microscopy -
correct answer ✅The specimen is often darker than the
background because the specimen with a thickness slows down the
phases of light waves creating contrast and thus is darker against a
white background.
Thick biological specimens can be used where light cannot transmit
through thick regions compared to the thin regions, creating a
contrast without stain (but not as great with a stain). However, if
you have a biological sample that is thin and usually has a clear
cytoplasm, then one must use a stain to enhance contrast of image.
Darkfield microscopy -
correct answer ✅The specimen is lighter against the darker
background.
, MIMG 105 Midterm Exam Questions &
Answers (Grade A+)
One uses a spider-light stop plate where the center blocks the
central beam of light(high-pass filter and thus blocks the
background) and so light from the edges scatter when passing
through the condenser lens onto the specimen, shining light onto
the specimen against a dark background.
Since the physical filter allows one to see the sample with high
contrast due to phase contrast, the samples observed can be alive
(no need to stain them!)
Phase Constrast Microscopy -
correct answer ✅This uses a zernike phase plate (pinhole aperture
in the middle) to let central unscattered light converge on the focal
point in the plane while the scattered light is blocked by the
thickness of the plate (absorbed and doesn't go through).
Therefore, the phase of the light waves differ by pi/2 by the
specimen and then by the plate by pi/2 as well (values may differ)
so that eventually a 180 degree phase difference occurs, leading to
constructive and destructive interference when summing the two
waves.
Answers (Grade A+)
Sensitivity -
correct answer ✅Actually being able to see your object (if it's in
the field of view)
Specificity -
correct answer ✅Being able to identify certain objects in the
image. Commonly present in LM with fluorescence microscopy and
in TEM obtaining specificity is only possible with immunogold
particles that are specific to the antigens of interest. Can use
polyclonal or monoclonal.
Contrast -
correct answer ✅Being able to distinguish an object from its
background
Resolution -
correct answer ✅The minimum distance required to differentiate
between objects. Higher resolution means smaller numbers in nm.
What are the key properties of a microscope? -
correct answer ✅Wave: Must determine what particles to use to
determine wavelength and eventually the resolution of the final
image. Photons of visible light (400-700nm) >neutrons
,MIMG 105 Midterm Exam Questions &
Answers (Grade A+)
Lens: one would need a lens with a suitable numerical aperture to
let a beam of light or electrons through and to bend the waves for it
to converge onto a focal point. The lens has a specific focal length
(it's different for every lens). Magnification: producing an enlarged
image
Brightfield Microscopy -
correct answer ✅The specimen is often darker than the
background because the specimen with a thickness slows down the
phases of light waves creating contrast and thus is darker against a
white background.
Thick biological specimens can be used where light cannot transmit
through thick regions compared to the thin regions, creating a
contrast without stain (but not as great with a stain). However, if
you have a biological sample that is thin and usually has a clear
cytoplasm, then one must use a stain to enhance contrast of image.
Darkfield microscopy -
correct answer ✅The specimen is lighter against the darker
background.
, MIMG 105 Midterm Exam Questions &
Answers (Grade A+)
One uses a spider-light stop plate where the center blocks the
central beam of light(high-pass filter and thus blocks the
background) and so light from the edges scatter when passing
through the condenser lens onto the specimen, shining light onto
the specimen against a dark background.
Since the physical filter allows one to see the sample with high
contrast due to phase contrast, the samples observed can be alive
(no need to stain them!)
Phase Constrast Microscopy -
correct answer ✅This uses a zernike phase plate (pinhole aperture
in the middle) to let central unscattered light converge on the focal
point in the plane while the scattered light is blocked by the
thickness of the plate (absorbed and doesn't go through).
Therefore, the phase of the light waves differ by pi/2 by the
specimen and then by the plate by pi/2 as well (values may differ)
so that eventually a 180 degree phase difference occurs, leading to
constructive and destructive interference when summing the two
waves.
