Today’s Learning outcomes. : Today’s Learning outcomes. You Should be able to understand the refraction from lenses.
You should be able to understand principal axis, focal point, focal length, vertical axis .
Converging/Diverging lens.
Image formation by lenses.
What You Should Know. : What You Should Know. Basic Idea of Refraction of light.
Basic knowledge of ray optics.
Basic knowledge of geometry.
Lens : Lens If a piece of glass or other transparent material takes on the appropriate shape, it is possible that parallel incident rays would either converge to a point or appear to be diverging from a point. A piece of glass which has such a shape is referred to as a lens.
Converging Lens : Converging Lens
Diverging Lens : Diverging Lens
Important Terms Used : Important Terms Used If a symmetrical lens is thought of as being a slice of a sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the lens. This imaginary line is known as the principal axis
A lens also has an imaginary vertical axis which bisects the symmetrical lens into halves. As mentioned above, light rays incident towards either face of the lens and traveling parallel to the principal axis will either converge or diverge.
Slide 7 : If the light rays converge (as in a converging lens), then they will converge to a point. This point is known as the focal point of the converging lens Technically, a lens does not have a center of curvature (at least not one which has any importance to our discussion). However a lens does have an imaginary point which we refer to as the 2F point. This is the point on the principal axis which is twice as far from the vertical axis as the focal point is.
Slide 8 :
Refraction Rules for a Converging Lens : Refraction Rules for a Converging Lens Any incident ray traveling parallel to the principal axis of a converging lens will refract through the lens and travel through the focal point on the opposite side of the lens.
Any incident ray traveling through the focal point on the way to the lens will refract through the lens and travel parallel to the principal axis.
An incident ray which passes through the center of the lens will in affect continue in the same direction that it had when it entered the lens.
Refraction Rules for a Diverging Lens : Refraction Rules for a Diverging Lens Any incident ray traveling parallel to the principal axis of a diverging lens will refract through the lens and travel in line with the focal point (i.e., in a direction such that its extension will pass through the focal point).
Any incident ray traveling towards the focal point on the way to the lens will refract through the lens and travel parallel to the principal axis.
An incident ray which passes through the center of the lens will in affect continue in the same direction that it had when it entered the lens.
Image formation by converging Lens : Image formation by converging Lens
Check your understanding : Check your understanding Q1.Lens is a refracting surface(T.F)
Q2.There are two types of lenses(Diverging,Converging)(Y,N)
Q3.Focal length of a lens is the distance of lens from object.(T.F.)
Q4. Light travell parallel to principal axix emerged out from a lens meet at principal point.(T.F.)
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