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LENSES

Gejala mereka yang mengalami rabun dekat: Kuman di ‘over sea’nampak, gajah ‘termenung’ tak nampak

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Focal Point & Focal Length of a Lens (CONVEX LENS)

Opticalcentre

Focus, F

Focal length,f 

Opticalcentre

Focus, F

Focal

length, f 

!uestion:

a) What happen to the light after passes through the lens

!) Na"e the pheno"enon of light #hich occurre$%

c) What are the $ierences !et#een the lens

$) What is the relationship !et#een the thic'ness of the lens

an$ its focal length

"igure #a$ "igure #b$

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Optical centre,

C

Focus, F

Focallength, f

( e)

*uestion+

a$ Name the type o% lensb$ &hat is happen to the light a%ter passes through the lens'

($ &hy the %o(al length is signed as negative'

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Lens 

Lens- 

Question:

a$ Name the phenomenon o% light )hi(h o((urred

b$ *ompare the (hara(teristi( o% images )hi(h %ormed by lens + andlens

O!.ect

&hat are you looking through the lens is aimages

Cone/Lens

ConcaeLens

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How to Draw Rays Diagram?

Principal axis

Convex lens

F F2F 2FObject

u

Image

v

f

Focal

point

a) u 0 1f2 ( E/a"ple+ 3ien that f 4 56 c"2u 4 17 c")

- .he (hara(teristi( o% image:

/eal, inverted 0 diminished

1 Linear magni2(ation, m 3 height o% image 4 height o%obje(t 3 v 4 u

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F F2F

2F

Object

a) u 4 1f2 (u 4 16c") 8eal, inerte$ & sa"e

si9e

F   F2F

2F

O

!) f : u : 1f2 (u 457 c")

8eal, inerte$ &"agni;e$

Image

I

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F F2F

2F

c) u 4 f2 (u 4 56c") Virtual, upright, i"age at

in;nit< & "agni;e$

Object

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F F

2F

O

a) u : f2 (u 4 7 c")

Virtual, upright &

"agni;e$

u

-v

Linear "agni;cation, " 4 height of i"age = height ofo!.ect 4 = u

" is negatie (")

I

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Figure a: >he !oo'$istance, u is !igger than

focal point, f%

Figure b: >he !oo'$istance, u is s"aller thanfocal point, f%

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?ni !aru @i"e.A,!elu" @o!.e'A

se!enar%

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Principal axis

Concave lens

F FO

u

I

-v

-f

- .he (hara(teristi( o% image:

5irtual, upright 0 diminished

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