PhysicsUK
THE OPTICAL BENCH

Lens & Ray Diagram Lab

START HERE · GCSE

Find a sharp image

Move the screen until the arrow is sharp.

Drag the object, lens or screen · ruler handles measure distance
Parallel rayCentre rayFocal rayDashed = backward extension
Object distance, u50.0 cm
Screen from optic48.0 cm
Blur at screen—
Ruler distance50.0 cm
Calculated imageHidden
CHOOSE AN INVESTIGATION

What will you discover?
BUILD & ADJUST

Your optical bench

Drag on the bench, use arrow keys for the selected apparatus, or enter exact positions here. Positions are measured from the bench zero.

Reveal Image & backward extensions to inspect calculated image position, height and magnification.

In Draw rays mode, automatic rays and calculated images stay hidden until you choose Show solution. Switch to Explore to drag apparatus, or edit its properties here. The screen is a schematic off-axis observation plane for mirrors; it does not block the incident beam.

Setup and notebook are saved on this device.
OBSERVE · MEASURE · EXPLAIN

Find a sharp image

    ORIGINAL EXAM-STYLE QUESTION

    Show mark scheme

    Self-assess your answer against each marking point. Numerical questions refer to the stated setup; Reset restores it.

    Think about this
    ALTERNATIVE TO POINTING

    Construct with coordinates

    The incoming ray begins at the object tip. Choose its height at the optic, then a point on its outgoing path. Coordinates use the bench zero; positive height is above the axis.

    Place the image tip using the same coordinate system.
    YOUR EXPERIMENTAL EVIDENCE

    Notebook

    Capture records the apparatus and screen observation. An image distance and focal-length estimate are recorded only when the screen is focused. Changing the bench never changes a saved reading.
    USING THE LAB

    Light, images & measurements

    Make your first measurement

    Move the screen until its image is sharp. The screen view shows the blur made by rays from the arrow tip. Capture a reading, move the object, and focus again.

    Draw your own rays

    Choose a principal ray. Click where it meets the optic, then along its outgoing path. The start is the object tip. Draw at least two different rays, check them, then place the image tip where they or their backward extensions meet. Dashed lines are geometrical constructions, not light travelling backwards. Keyboard drawing provides equivalent numerical controls.

    Controls

    Drag apparatus or ruler handles. Select an item in the bottom bar, focus the bench and use ← / → to move 1 cm (Shift: 0.1 cm). For the object, ↑ / ↓ changes its height. Escape cancels a drag or an unfinished ray. Pan and zoom change only the view. Fit includes finite images where practical; very distant images remain labelled off the bench.

    Model & conventions

    One ideal thin lens or paraxial spherical mirror, one upright real object, in air. Distances are stored in metres and displayed in centimetres. Positive u is object-to-optic distance. Positive v is along the outgoing light direction; negative v denotes a virtual image. Converging lenses and concave mirrors have positive f; diverging lenses and convex mirrors have negative f.

    1/f = 1/u + 1/v   ·   m = −v/u

    Finite aperture clips rays. Aberrations, diffraction, intensity calibration and wave effects are omitted. The screen is an observation plane, not an opaque obstacle; for a mirror it represents an off-axis screen so incident rays are not blocked. Screen blur is the geometrical spread of a point-source bundle through the full aperture; “sharp” means spread ≤ 3 mm. Ruler readings resolve 1 mm. Ideal image height and position are predictions, not screen measurements. Trace light is a slowed construction illustration, not a measurement of light speed.

    Course guidance

    Lens image formation and magnification support GCSE Physics. Lens-equation calculations, focal-length measurement and curved mirrors are labelled extension/enrichment; their inclusion is not a claim that every AQA or OCR course requires them.

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