- Lenses
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Objectives:
- To be able to explain how convex lenses can help short-sightedness
Timing: 1-2 lessons
Lenses refract light to a focal point. Draw diagrams to show how convex or converging lenses do this to diverging and parallel beams of light. The following sites may help you: http://acept.la.asu.edu/PiN/mod/light/lenses/pattLight2Obj2.html and http://www.opticalres.com/optics_for_kids/kidoptx_p2.html.
Your teacher will probably get you to carry out an experiment to measure the focal distances of different lenses.
Explain how convex lenses are used in cameras, projectors and magnifying glasses to produce real (and inverted) and virtual images. You need to be able to draw ray diagrams to show this. Also find out the formula for magnification.
There are also a couple of lenses games at: http://www.iknowthat.com/com/L3?Area=Projectile and http://www.iknowthat.com/com/L3?Area=OpticsWorkbench and an activity at: http://lectureonline.cl.msu.edu/~mmp/applist/optics/o.htm.
Now read about short-sightedness and how convex lenses are used to correct it: http://www.patient.co.uk/showdoc/23069162/ and http://hcd2.bupa.co.uk/fact_sheets/html/myopia.html.
You could do the following worksheet:
