1. What Is Optical Resolution?

Optical resolution refers to the ability of an optical system to distinguish between two closely spaced objects. It represents the minimum distance at which two points can be distinguished as separate entities rather than a single blurred point.

2. How Resolution Is Calculated

The optical resolution limit is calculated using the formula:

Where:

• \( NA \) — Numerical aperture (unitless)
• \( n \) — Refractive index of the medium (unitless)
• \( \lambda \) — Wavelength of light (meters)

Explanation: This formula, derived from the Abbe diffraction limit, describes the fundamental limit of resolution in optical microscopy systems. The resolution improves (smaller value) with higher numerical aperture, higher refractive index, and shorter wavelength.

3. Importance of Resolution Calculation

Details: Understanding optical resolution is crucial for designing microscopy systems, evaluating imaging performance, and determining the limits of what can be observed at microscopic scales. It helps scientists and engineers optimize optical systems for specific applications.

4. Using the Calculator

Tips: Enter numerical aperture (typically 0.1-1.4), refractive index of the medium (1.0 for air, ~1.33 for water, ~1.52 for glass), and wavelength in nanometers (400-700 nm for visible light). All values must be positive and within reasonable physical limits.

5. Frequently Asked Questions (FAQ)

Q1: What is numerical aperture (NA)?
A: Numerical aperture is a dimensionless number that characterizes the range of angles over which the system can accept or emit light. Higher NA means better light gathering ability and resolution.

Q2: How does wavelength affect resolution?
A: Shorter wavelengths (blue/violet light) provide better resolution than longer wavelengths (red light) because diffraction effects are reduced at shorter wavelengths.

Q3: What is the typical resolution range for optical microscopes?
A: Conventional optical microscopes typically achieve resolutions around 200-500 nm, while super-resolution techniques can reach below 100 nm.

Q4: Can resolution be better than this calculated limit?
A: This formula represents the diffraction limit for conventional microscopy. Super-resolution techniques like STED, PALM, and STORM can achieve better resolution by using special methods.

Q5: How does immersion oil improve resolution?
A: Immersion oil has a higher refractive index (~1.52) than air, which increases the numerical aperture and thus improves resolution by reducing light refraction at the interface.