Q.99 According to Abbe’s equation on microscopy, the ability to resolve two entities
inside a cell by light microscopy depends on which of the following factor/s?
(A) Magnification of the objective lens
(B) Intensity of incident light
(C) Wavelength
(D) Numerical aperture of the objective lens
Abbe’s equation determines the resolution limit in light microscopy, primarily depending on wavelength and numerical aperture. The correct answer is (C) Wavelength and (D) Numerical aperture of the objective lens.
Option Analysis
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(A) Magnification of the objective lens: Magnification enlarges the image but does not improve the ability to distinguish two close entities; empty magnification occurs without sufficient resolution.
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(B) Intensity of incident light: Higher intensity improves visibility and contrast but does not affect the fundamental diffraction-limited resolution.
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(C) Wavelength: Shorter wavelengths (λ) in Abbe’s equation d = λ/(2NA) reduce the minimum resolvable distance d, enhancing resolution.
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(D) Numerical aperture of the objective lens: Higher NA (n sin α) in the denominator increases resolution by capturing more diffracted light rays.
Abbe’s Equation Explained
Abbe’s diffraction limit formula is d = λ/(2NA), where d is the smallest resolvable distance, λ is light wavelength, and NA is numerical aperture (refractive index n times sin of half-angle α). For cellular imaging, typical green light (λ ≈ 550 nm) with NA 1.4 yields d ≈ 200 nm, below which structures blur due to diffraction. Axial resolution follows d = 2λ/NA², further emphasizing λ and NA.
Light microscopy resolution hinges on Abbe’s equation microscopy resolution factors like wavelength and numerical aperture, crucial for distinguishing entities inside cells. This guide breaks down the formula d = λ/(2NA), ideal for CSIR NET Life Sciences aspirants tackling competitive exam questions on microscopy limits.
Core Resolution Factors
Abbe’s equation microscopy resolution factors include:
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Wavelength (λ): Shorter λ (e.g., blue light over red) shrinks resolvable distance, bypassing diffraction barriers.
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Numerical Aperture (NA): NA = n sin α boosts light collection; oil immersion objectives (NA >1.4) achieve ~200 nm lateral resolution.
Magnification and light intensity play no direct role in Abbe’s limit.
Practical Applications in Cell Biology
In cellular imaging, Abbe’s equation microscopy resolution factors limit visualization of organelles like mitochondria (~500 nm) but fail sub-200 nm structures without super-resolution techniques. For exams, remember: resolution improves via UV light or high-NA lenses.
