c urved lenses 13.1, 13.3, 13.4. d iverging lens, c oncave shape f

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