c urved lenses 13.1, 13.3, 13.4. d iverging lens, c oncave shape f
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CURVED LENSES13.1, 13.3, 13.4
DIVERGING LENS, CONCAVE SHAPE
F
CONVERGING LENS, CONVEX SHAPE
PATH DEVIATION
Air to glass – bends towards the normal
Glass to air – bends away from normal
RAY CONVERGES
NOTICE THAT THE DEVIATION OF THE LIGHT RAY (X) INCREASES IF THE THICKNESS OF THE LENS INCREASES
X
F2F F 2F
O
object
OPTICAL CENTRE
2F’ F’
LENS DIAGRAM SET UP
VIRTUAL FOCAL POINT
F2F F 2F
O
object
HOW DO WE KNOW WHICH SIDE IS REAL AND WHICH SIDE IS VIRTUAL?REMEMBER THAT PREVIOULY THE REAL SIDE IS WHEREVER THE OBSERVER WHO IS SEEING THE IMAGE IS LOCATED…WHEN DEALING WITH LENSES, WHICH SIDE IS THIS?
VIRTUAL REAL
OPTICAL CENTRE
2F’ F’
F2F F 2F
O
object
2F’ F’
RAY #1: Any ray that is parallel to the PA is refracted through the F
RAY #2: Any ray that pass through F is refracted parallel to PA
RAY #3: Any ray that passes through O continues through
USE SAME CONCEPTS AS THE ONES USED IN MIRRORS
SPECIAL CASES WITH CONVERGING LENSES (P. 377)
F2F F 2F
O
2F’ F’
Object beyond 2F’: image is real, inverted, smaller
F2F F 2F
O
2F’ F’
Object at 2F’: image is inverted, same size, real
F2F F 2F
O
2F’ F’
Object between F’ and 2F’: image is beyond 2F, real inverted, larger
F2F F 2F
O
2F’ F’
Object at F’: no image
Light rays remain parallel and don’t converge thus no image formed
F2F F 2F
O
2F’ F’
Object between lens and F’: image is virtual, erect, larger
RULES WITH DIVERGING LENSES
F2F F 2F
object
2F’ F’
RAY #1: Any ray that is parallel to the PA appears to be refracted through the F’
RAY #2: Any ray that appears to pass through F is refracted parallel to PA
RAY #3: Any ray that passes through O continues through