For a thin double convex lens, refraction acts to focus all parallel rays to a point referred to as the principal focal point. The distance from the lens to that point is the principal focal length f of the lens. For a double concave lens where the rays are diverged, the principal focal length is the distance at which the back-projected rays would come together and it is given a negative sign. The lens strength in diopters is defined as the inverse of the focal length in meters. For a thick lens made from spherical surfaces, the focal distance will differ for different rays, and this change is called spherical aberration. The focal length for different wavelengths will also differ slightly, and this is called chromatic aberration.

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Focallength formula

MO-EL S.p.A.MO-EL has been manufacturing electrical products for over 40 years. Famous for the CRI CRI model, the most effective and robust insect trap ever, the MO-EL electroinsecticide range includes the suction Insectivoro system and adhesive paper devices.

The principal focal length of a lens is determined by the index of refraction of the glass, the radii of curvature of the surfaces, and the medium in which the lens resides. It can be calculated from the lens-maker's formula for thin lenses.

The most important characteristic of a lens is its principal focal length, or its inverse which is called the lens strength or lens "power". Optometrists usually prescribe corrective lenses in terms of the lens power in diopters. The lens power is the inverse of the focal length in meters: the physical unit for lens power is 1/meter which is called diopter.

This shows parallel beams from two helium-neon lasers converging to the principal focal point of a 30 cm double convex lens. The rays then enter a diverging lens of focal length -10cm on the right. The laser beams were made visible with a spray can of artificial smoke.

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Focallength

MO-EL S.p.A.MO-EL has been manufacturing electrical products for over 40 years. Famous for the CRI CRI model, the most effective and robust insect trap ever, the MO-EL electroinsecticide range includes the suction Insectivoro system and adhesive paper devices.

The heaters that use this technology offer instant heat, are extremely efficient and even in the presence of drafts keep their performance unchanged. In fact, short waves do not disperse heat in the air, but only heat surfaces exposed to heating rays. The MO-EL IR-A heaters have no glass, and for this reason they convert about 99.9% of the electric current into heating rays. Their brightness varies from model to model. The range of action is explained by the light beam, in fact they behave exactly like the sun’s rays. They are particularly suitable for very large spaces or outdoors, where they allow to create heat zones even in the presence of drafts.

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Whether in public places, places of worship, terraces, production sites or domestic environments,in the MO-EL catalog you will find the right solution for heating and disinfestation.

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