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Optical Methods > Exam (only question) > Flashcards

Exam (only question) Flashcards

1
Q

In a brightfieldmicroscope, which component ensures that the illumination light is collected and guided onto the specimen?

A

Condenser lens

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2
Q

In which type of microscopes is the birefringence (anisotropy) of a structure detected?
dt. Bei welcher Art von Mikroskopen wird die Doppelbrechung (Anisotropie) einer Struktur nachgewiesen?

A

Polarization microscope

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3
Q

Which principle do light microscopes use to form an image visible to the eye under ultraviolet illumination?

A

Fluorescence

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4
Q

How are field of view and resolution usually related in a microscopic image?

A

The larger the magnification of the objective, the smaller the field of view.

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5
Q

What physical laws govern photophysics?

A

The quantization of all energy states as described by quantum mechanics

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6
Q

What is the advantage of fluorescent dyes with a large Stokes shift?

A

Easier separation of excitation and fluorescence radiation

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7
Q

What are common features of confocal microscopy (CM) and structured illumination microscopy (SIM).

A

Both increase resolution compared to classical microscopy

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8
Q

What is called deconvolution in microscopy?

A

The consideration of the effect of the point spread function(PSF) on imaging

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9
Q

What mathematical transformation connects the light fields in the image and aperture planes?

A

Fourier transform

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10
Q

Which statement about total internal reflection fluorescence microscopy (TIRF) is correct?

A

Due to the total reflection of the excitation laser light, the fluorescence is excited by an evanescent field within a layer of only 200 nm thickness, so that the axial resolution in TIRF can be very high.

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11
Q

What does the STED stand for in the super-resolution microscopy developed by Stefan Hell?

A

STED = Stimulated Emission Depletion

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12
Q

What is the advantage of fluorescence lifetime imaging microscopy (FLIM)?

A

It enables observation of the local environment of the fluorescence molecules.

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13
Q

What is an important advantage of two-photon microscopy over confocal microscopy for in vivo imaging?

A

The longer wavelength achieves a deeper penetration depth.

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14
Q

What is time-correlated single-photon counting (TCSPC)?

A

It accumulates single-photon arrival times in a histogram to determine the fluorescence decay time.

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15
Q

How does Raman spectroscopy enable us to make statements about the structure of molecules?

A

Because certain subgroups of molecules often have well separable and characteristic Raman bands.

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16
Q

What is the main problem with Raman spectroscopy?

A

The Raman scattering cross section is typically very small.

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17
Q

What role do visualization methods play in modern microscopy?

A

Visualization of complex 3-dimensional relationships in the sample

18
Q

By which process can intracellular nanosurgery be realized with laser light in cells that are actually transparent?

A

Strong focusing of a laser pulse results in optical breakdown at the focus, where an expanding cavitation bubble disrupts the surrounding structures.

19
Q

Which characteristic of electrons is used for imaging in electron microscopy?

A

Electrons have at sufficiently high kinetic energy a short wavelength (de-Broglie), which is relevant for the resolution.

20
Q

Why are the samples for scanning electron microscopy (SEM) often coated with a thin layer of gold?

A

Because a local charging of the sample by the electron beam must be avoided, as this would have a negative effect on the SEM image.

21
Q

What is the role of the objective lens and if present the tube lens?

A

Objective lens and tube lens have to bring all beams from one object point to one corresponding point in the intermediate image plane.

22
Q

How to reduce the negative influence of chromatic aberrations in a brightfieldmicroscope when working with white illumination light?

A

By means of apochromatic objective lenses.

23
Q

Prisms in the optical path of an upright microscope allow for inclined views. Why is this an advantage?

A

Despite a comfortable body posture, the object table remains horizontally.

24
Q

What is a disadvantage when using immersion fluid?

A

Can only be used with special, fluid tight objective lenses.

25
Q

How do the absorption and fluorescence spectra of a dye differ?

A

The fluorescence spectrum is shifted to longer wavelengths.

26
Q

What special properties of fluorescent proteins are exploited for fluorescence microscopy?

A

Proteins that cells express can be labeled.

27
Q

What component is in a fluorescence microscope indispensable?

A

A wavelength selective filter

28
Q

What is the advantage of a photomultiplier in the detection of fluorescence signals?

A

High detection sensitivity.

29
Q

What are the advantages of structured illumination in fluorescence microscopy?

A

Optical sectioning is possible

30
Q

Which statement about super resolution in STED microscopy is correct?

A

The spatial resolution can be better, …
… the higher the intensity of the depletion laser.

31
Q

Which statement about super-resolution with PALM is correct?

A

The method relies on multiple excitation of spatially separated and photoactivatable fluorescent proteins.

32
Q

What is the fluorescence lifetime in FLIM microscopy?

A

The time where the fluorescence signal has decayed to 1/e-times its’ peak amplitude.

33
Q

While imaging a thick tissue sample with a confocal fluorescence microscope your sample bleaches. How can you improve the experiment?

A

By employing two-photon microscopy the bleaching can be lowered significantly.

34
Q

What is special about the second-harmonic generation (SHG) light?

A

It is generated at exactly half of the excitation wavelength.

35
Q

Why are lasers also used for spontaneous Raman spectroscopy?

A

Because lasers can emit very narrowband light.

36
Q

What is the advantage of CARS microscopy?

A

In some cases relatively high signal intensities can be achieved.

37
Q

How can 3-dimensional fluorescence microcopy data be visualized?

A

Display of the maximum of the fluorescence along the line of sight (maximum intensity projection)

38
Q

Why are high intensities required for intracellular nanosurgeryby femtosecond laser-induced optical breakdown?

A

Because high intensities are required for nonlinear energy deposition.

39
Q

Which of the following statement is not true for both transmission electron microscopy (TEM) and scanning electron microscopy (SEM)?

A

The specimen must be prepared in thin sections.

40
Q

What is one difference between the specimen preparation for a transmission electron microscope (TEM) and a scanning electron microscope (SEM) under vacuum conditions?

A

Only the SEM specimen requires sputter coating.

Optical Methods (2 decks)

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