Optical Microscopy Resolution Factors
The spatial resolution in optical microscopy, which is the smallest distance between two points that can be distinguished as separate, is primarily determined by the wavelength of light used and the numerical aperture (NA) of the objective lens.
The relationship is described by the Abbe diffraction limit formula:
$ d = \frac{\lambda}{2 \times NA} $Where:
- $d$ is the minimum resolvable distance (resolution)
- $\lambda$ is the wavelength of the illuminating light
- $NA$ is the numerical aperture of the objective lens
To achieve the best spatial resolution (i.e., the smallest possible value for $d$), we need to:
- Minimize the wavelength ($\lambda$).
- Maximize the numerical aperture ($NA$).
Resolution Analysis of Options
Let's analyze the options based on these principles:
- Option 1: $\lambda = 400$ nm, NA = 1.0. Resolution is proportional to $400 / 1.0 = 400$.
- Option 2: $\lambda = 600$ nm, NA = 1.2. Resolution is proportional to $600 / 1.2 = 500$.
- Option 3: $\lambda = 400$ nm, NA = 1.2. Resolution is proportional to $400 / 1.2 \approx 333.3$.
- Option 4: $\lambda = 600$ nm, NA = 1.0. Resolution is proportional to $600 / 1.0 = 600$.
Comparing the proportional values ($400$, $500$, $333.3$, $600$), the smallest value ($\approx 333.3$) corresponds to the best spatial resolution.
Conclusion
The combination providing the best spatial resolution is the one with the shortest wavelength and the highest numerical aperture.
Therefore, $\lambda = 400$ nm and NA = 1.2 offers the superior resolution.
Important Questions from Microstructure Ferrite Pearlite Cementite Fraction
- A 0.2 wt.% plain carbon steel sheet is heated and equilibrated in the inter-critical region followed by instant water quenching. The microstructure of the quenched steel sheet consists of
- Which one of the following crystal structure changes occurs during the transformation of mild steel from austenite to martensite?
Magnesium treatment is carried out to produce ______________ cast iron.
- With increase in carbon content (up to 2 mass%) in Fe-C alloy, which one of the following statements is correct with respect to the lattice parameters ($c$ and $a$) of BCT martensite?
- In a typical scanning electron microscope (SEM) image, information about topography and atomic contrast are obtained from ________.
