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Introduction to Lenses. Definition of a lens. A lens is transparent piece of plastic or glass with at least one refractive surface. How do lens work. A lens works by refracting (bending) light rays as they pass through it so they change direction
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Definition of a lens • A lens is transparent piece of plastic or glass with at least one refractive surface.
How do lens work • A lens works by refracting (bending) light rays as they pass through it so they change direction • Lenses work by bendinglight at a glass-air boundary. Although refraction occurs at the boundary, we will treat all lenses as bending the rays at the lens axis.
Converging Lens • The lens in the eye is a convex or converging lens. This means that the lens makes rays of light come together, or converge.
Converging Lens • The rays parallel to the principal axis are converged onto the principal focus. • The focal length is the distance between the lens axisand the principal focus.
Diverging Lens • The concave lens cause rays traveling parallel to the principal axis to diverge, which is why it is called a diverging lens. • The principal focus is virtual because the rays do not pass through it, but diverge as if they had come from it.