OpticsIntermediateStarter track

Concept module

Optical Resolution / Imaging Limits

Image two nearby point sources through one finite aperture and see why diffraction, wavelength, and aperture diameter limit how sharply an optical system can separate them.

Interactive lab

Keep the stage, graph, and immediate control feedback in one working view.

A finite aperture turns each point into a diffraction blur. Aperture, wavelength, and source separation all stay tied to the same detector profile.

Live setup

Resolution state

theta_R: 0.28 mrad
Delta theta: 0.32 mrad
ratio: 1.14
dip / peak: 0.51
sample: 0.51

The pair is near the Rayleigh threshold, so the split is just beginning to show.
Airy radius on the image plane is about 33.55 um while the point spacing is 38.4 um.

Graphs

Switch graph views without breaking the live stage and time link.

Image-plane profile

Shows the combined detector profile and the two individual point-spread contributions for the current aperture-limited image.

image-plane height (um): -180 to 180normalized exposure: 0 to 1

Combined exposurePoint A spreadPoint B spread

Hover or scrub to link the graph back to the stage.image-plane height (um) / normalized exposure

Controls

Adjust the physical parameters and watch the motion respond.

Wavelength

l amb d a

550 nm

Longer wavelength broadens each point-spread blur.

Aperture diameter

D

2.4 mm

A larger clear aperture improves resolving power by shrinking the diffraction pattern.

Point separation

D e l t a t h e t a

0.32 mrad

Sets how far apart the two object points are in angle.

Detector sample

y_{d}

0 um

Moves the live sample point along the detector profile.

More tools

Secondary controls, alternate presets, and less-used toggles stay nearby without crowding the main bench.

Show

More presets

Presets

Predict -> manipulate -> observe

Keep the active prompt next to the controls so each change has an immediate visible consequence.

Graph readingPrompt 1 of 2

Notice that the graph is a detector-position profile, not a time trace. Hovering it previews where the sample sits on the image plane right now.

Try this

Hover the profile near the center dip, then near one peak, and compare the live detector sample readout.

Equation map

See each variable before you move it.

Select a symbol to highlight the matching control and the graph or overlay it most directly changes.

l amb d a

Wavelength

550 nm

Longer wavelengths broaden the diffraction blur, so nearby points become harder to distinguish.

Graph: Image-plane profileOverlay: Rayleigh guide

Equations in play

Choose an equation to sync the active symbol, control highlight, and related graph mapping.

More tools

Detailed noticing prompts, guided overlays, and challenge tasks stay available without taking over the main bench.

Hide

What to notice

Use one prompt at a time so the aperture, the detector strip, and the graph stay tied to the same live resolution story.

Graph readingPrompt 1 of 2

Graph: Image-plane profile

Notice that the graph is a detector-position profile, not a time trace. Hovering it previews where the sample sits on the image plane right now.

Try this

Hover the profile near the center dip, then near one peak, and compare the live detector sample readout.

Why it matters

Resolution lives in the spatial profile across the detector, not in a later-versus-earlier time story.

Graph: Image-plane profile

Guided overlays

Focus one overlay at a time to see what it represents and what to notice in the live motion.

2 visible

Overlay focus

Aperture guide

Marks the clear aperture diameter directly on the lens.

What to notice

The finite opening is part of the imaging physics. Changing D changes the diffraction width itself rather than only scaling the brightness.

Why it matters

It keeps resolving power attached to the aperture geometry instead of treating blur as a mysterious screen effect.

Control: Aperture diameterGraph: Image-plane profileEquation

D

Challenge mode

Use the real aperture-limited detector profile to hit resolution targets instead of switching to a detached puzzle model.

0/2 solved

TargetCore

2 of 4 checks

Hit the Rayleigh threshold

Starting from Blurred pair, tune the aperture or wavelength until the point spacing sits right on the Rayleigh limit.

Graph-linkedGuided start

Suggested start

Use the Rayleigh guide and the profile dip together.

Matched

Open the Image-plane profile graph.

Image-plane profile

Matched

Keep the Rayleigh guide visible.

Pending

Bring Delta theta / theta_R between 0.97 and 1.03.

1.14

Pending

Keep the center-to-peak ratio between 0.7 and 0.9.

0.51

The checklist updates from the live simulation state, active graph, overlays, inspect time, and compare setup.

With wavelength 550 nm and aperture 2.4 mm, the Rayleigh limit is about 0.28 mrad. The current point separation is 0.32 mrad, which is 1.14 times that limit. The pair is near the Rayleigh threshold.

Equation detailsDeeper interpretation, notes, and worked variable context.

Rayleigh limit

Two equally bright point sources become hard to distinguish when their angular separation falls below this diffraction-limited scale.

θ_{R} \approx 1.22 \frac{λ}{D}

l amb d a

Wavelength 550 nm

D

Aperture diameter 2.4 mm

Image-plane spacing

At fixed focal length, angular separation maps to detector spacing.

s \approx f Δ θ

D e l t a t h e t a

Point separation 0.32 mrad

y_{d}

Detector sample 0 um

Image-plane blur radius

The same diffraction limit can be read as the characteristic size of one point-spread core on the detector.

r_{R} = f θ_{R} \approx 1.22 \frac{λ f}{D}

l amb d a

Wavelength 550 nm

D

Aperture diameter 2.4 mm

Progress

Not startedMastery: NewLocal-first

Start exploring and Open Model Lab will keep this concept's progress on this browser first. Challenge mode has 2 compact tasks ready. No finished quick test, solved challenge, or completion mark is saved yet.

Let the live model runChange one real controlOpen What to notice

Try this setup

Copy the live bench state and reopen this concept with the same controls, graph, overlays, and compare context.

Stable links

Starter track

Step 5 of 50 / 5 complete

Wave Optics

Earlier steps still set up Optical Resolution / Imaging Limits.

1. Polarization2. Diffraction3. Double-Slit Interference4. Dispersion / Refractive Index and Color+1 more steps

Previous step: Dispersion / Refractive Index and Color.

Start from track beginning

Short explanation

What the system is doing

An imaging system does not send each object point to a mathematically perfect point on the detector. A finite aperture diffracts the light, so each point becomes a blur pattern with a finite width.

This page keeps that story bounded on purpose: two equal point sources, one finite lens aperture, and one detector strip. The same wavelength, aperture diameter, point separation, and detector sample drive the stage, the profile graph, the overlays, the worked examples, the prediction prompts, the challenge checks, and the quick test so imaging limits stay tied to one honest diffraction-limited picture instead of a giant Fourier-optics platform.

Key ideas

01Resolution is limited because finite apertures diffract light. Even a well-focused lens turns one point into a spread pattern with a nonzero width.

02A larger aperture improves resolution by shrinking the diffraction blur, while a longer wavelength worsens resolution by broadening it.

03The Rayleigh limit theta_R approximately equals 1.22 lambda / D for a circular aperture, so two points become harder to distinguish when their angular separation falls below that scale.

Live worked example

Solve the exact state on screen.

Use the current aperture-limited imaging state directly. These substitutions stay attached to the live detector profile instead of switching to a detached worksheet.

Live valuesFollowing current parameters

For the current wavelength lambda = 550 nm and aperture D = 2.4 mm, what Rayleigh limit follows for two equal point sources?

l amb d a

Wavelength

550 nm nm

D

Aperture diameter

2.4 mm mm

t h e t a_{R}

Rayleigh limit

0.28 mrad mrad

1. Start from the Rayleigh estimate

Use

θ_{R} \approx 1.22 λ / D

for a circular aperture.

2. Substitute the live wavelength and aperture

\theta_R \approx 1.22 \dfrac{550 nm}{2.4 mm} = 0.28 mrad.

3. Map that blur scale onto the detector

With the fixed focal length, the same limit maps to an image-plane blur radius of 33.55 um.

Current Rayleigh limit

θ_{R} \approx 0.28 m r a d

and

r_{R} \approx 33.55 u m

The current pair is at or above the Rayleigh threshold, so the detector profile can sustain a visible dip between the peaks.

Common misconception

If the lens is focused correctly, two nearby points should always stay perfectly separate.

Correct focus removes defocus blur, but it does not remove diffraction from a finite aperture.

That is why nearby points can still merge when the aperture is small or the wavelength is long, even in an otherwise ideal imaging setup.

Mini challenge

You cannot move the object points, but you want the detector profile to show a clearer split. What is the best optical move?

Prediction prompt

Choose whether you should change aperture, wavelength, or detector sample position.

Check your reasoning

Increase the aperture or use a shorter wavelength so the diffraction blur shrinks.

Moving the detector sample only reads a different place on the existing image. The actual resolution limit changes when the aperture diameter or wavelength changes the diffraction width itself.

Quick test

Variable effect

Question 1 of 4

Answer from the live diffraction-limited imaging story, not from detached slogans.

Which change most directly improves resolving power for the same wavelength and object spacing?

Choose one answer to reveal feedback, then test the idea in the live system if a guided example is available.

Accessible description

The simulation shows two distant point sources on the left, one finite lens aperture in the middle, and one detector strip on the right. Each source sends light through the same aperture, and the detector strip brightens according to the combined diffraction-limited image profile.

Optional overlays show the aperture diameter on the lens, the current point-spread centers on the detector, and the Rayleigh blur scale around those centers. A movable detector sample marks one position on the strip and reports the current normalized exposure there.

Graph summary

The graph shows normalized exposure against detector height, with one combined profile and two dashed component profiles for the individual point-spread contributions.

Hovering the graph previews the matching detector position on the stage, so the spatial profile stays linked to the same image plane rather than turning into a detached time plot.

Keep moving through the concept map.

These suggestions come from the concept registry, so the reason label reflects either curated guidance or the fallback progression logic.

Another aperture patternOptics

Optical Resolution / Imaging Limits

See each variable before you move it.

Aperture guide

Hit the Rayleigh threshold

Wave Optics

What the system is doing

Solve the exact state on screen.

For the current wavelength lambda = 550 nm and aperture D = 2.4 mm, what Rayleigh limit follows for two equal point sources?

Which change most directly improves resolving power for the same wavelength and object spacing?

Keep moving through the concept map.

Double-Slit Interference

Lens Imaging

Diffraction