Complete guide to spherical lenses, mirrors, and image formation principles
Choose convex lens, concave lens, concave mirror, or convex mirror from the top-right dropdown.
Use sliders to change focal length (f), object distance (u), and object height (h). Ray diagram updates live.
Enable/disable parallel, central, and focal rays to understand light behaviour through lenses and mirrors.
Tap "Record Reading" to save observations. Switch to the Data tab to view tables and graphs.
Central point of a lens through which rays pass without deviation. Used as origin in Cartesian sign convention.
Geometric centre of a spherical mirror's reflecting surface. Origin for sign convention in mirror problems.
Where parallel rays converge (converging) or appear to diverge from (diverging) after refraction/reflection.
Distance from optical centre/pole to principal focus. Positive for converging, negative for diverging systems.
Distance of object from optical centre or pole. Always negative by new Cartesian sign convention.
Distance of image from optical centre or pole. Positive for real images (lenses). Opposite sign for mirrors.
• For lenses: Optical Centre (C) is the origin
• For mirrors: Pole (P) is the origin
• Light travels left to right (positive x-direction)
• All distances measured from the origin
Horizontal: Along incident light → +ve, against → −ve
Vertical: Upward → +ve, downward → −ve
u is always negative. Real image: v > 0 (lens), v < 0 (mirror).
Convex Lens
| Object Position | Image Position | Nature & Size |
|---|---|---|
| At infinity | At F | Real, inverted, highly diminished |
| Beyond 2F | Between F and 2F | Real, inverted, diminished |
| At 2F | At 2F (other side) | Real, inverted, same size |
| Between F and 2F | Beyond 2F | Real, inverted, magnified |
| At F | At infinity | Real, inverted, highly magnified |
| Between F and C | Same side as object | Virtual, erect, magnified |
Concave Mirror
| Object Position | Image Position | Nature & Size |
|---|---|---|
| At infinity | At F | Real, inverted, highly diminished |
| Beyond C | Between F and C | Real, inverted, diminished |
| At C | At C | Real, inverted, same size |
| Between F and C | Beyond C | Real, inverted, magnified |
| Between F and P | Behind mirror | Virtual, erect, magnified |
Two convex lenses (objective + eyepiece) to magnify microscopic specimens like cells and bacteria.
Convex lenses gather and magnify light from distant stars and planets.
Convex lenses focus light to form real, inverted images on sensor or film.
Convex for hypermetropia, concave for myopia — adjusting focal length.
Convex mirrors give wider field of view as side/rear-view mirrors.
Concave mirrors used close-up give magnified, erect virtual images of teeth.
Concave mirrors focus sunlight for solar cookers and power generation.
Concave mirrors with bulb at focus produce parallel beams for illumination.
| # | u (cm) | v (cm) | f (calc) | Error % |
|---|---|---|---|---|
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No observations yet.Go to Simulation and tap "Record Reading". |
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