Refraction of Light

REFRACTION

OF LIGHT

THE SUN RISE

The fish look bigger

Why is the sun look bigger if it is rising?Why is fish look bigger in the bottle? Why is some thing look bigger under the magnifying?

That it become, because :

RefractionOf light

Allah berfirman di dalam Al Qur’an : 24 ayat 39

Yang artinya :

Dan orang-orang yang kafir amalan-amalan mereka laksana fatamorgana di tanah yang datar yang disangka air oleh

orang yang dahaga, tapi bila didatanginya air itu dia tidak mendapatinya sesuatu

apapun.

Refraction Is The change direction or bending of

l ight at the inter face between two transparent media.

It occur when the speed of l ight changes

Look at the picture below !

Incident ray normal l ine

refracted ray• i = incident angle is the angle between the

incidence ray and normal to the surface at the incidence

• r = refracted angle is the angle between the refracted and the same normal

i

r

Refraction is caused by :The ray change speed.

Incidence ray

refracted ray

air

Glass

normal

air

Glass

normal

Incid

ence

ray

refracted

ray

air

Glass

normal

air

Glass

normal

Note

The rays enter more optically dense medium where they travel more slowly, the refracted rays bend toward the normal.The angle of refraction is smaller than the angle of incidence

The rays passes from more optically dense medium where they travel more quickly, the refracted rays bend away from the normal.The angle of refraction is bigger than the angle of incidence

Refraction is caused by :The ray change speed.

The ratio of speed c of light in vacuum to the speed v of light in medium is defined index of refraction (n)

C. vacuum------------V. Medium

n =

Table INDEX OF REFRACTION

Substance index of refractionGases

Air 1.000293Carbon dioxide 1.00045

LiquidsWater 1.333Ethyl alcohol 1.361

SolidsIce 1.309glass 1.6 – 1.9Diamond 2.419

Resume

1. If rays enter to more optically dense medium the refracted rays bend toward the normal

2. If rays exit from more optically dense medium the refracted rays bend backward the normal

Look at the figure !

Incidence ray normal

refracted ray

normal

refracted ray

Incidence ray

Refracted ray in the PLANPARALEL

Refraction 1

Refraction 2

displacement ray

Refraction on the prism

Deviation angle

Multiple refraction

Total internal reflection

This phenomena can use to explain (light propagating) fatamorgana

(light propagating) fatamorgana become light exit from dense medium

(light propagating) fatamorgana become if incidence angle more than critical angle

Critical angle is incidence angle that have refracted angle of 90o

Inter face

Dense Medium

Ik

Total internal reflection of light

Ik = critical angle is incidence angle that have refracted angle of 90o

Source light

Air more dense

Like surfaceof water

Surface of road

LENSES

Convex lenses (Magnifying Lenses)A glass which makes thing look bigger is use full in many ways. Watch makers, scientists and people who cannot see nearIt is thicker in the middle than at the edges. It can used to collect the rays of the sun on the spot, and in this way burn a hole in piece of paper.The spot where the sun’s ray collect is known focal point.The distance between the focal point and the lenses is called focal length.Lenses of different thickness have different focal length

LENSES

Concave lensesIt is thinner in the middle than at the edges. Parallel light rays which are passing trough a concave lens bend towards each other (diverging.In another word it is known diverging lens.

Convex lens

Bikonveks konkaf konveks plan konveks

Concave lens

Bikonkaf konveks konkaf plan konkaf

Look at the figure

Principal axix

We can make smo o th in e dg e

Part of Convex lens

Sumbu utamax x x xM1 F1 O F2 M2

R1

R2

F1 dan F2 = Focal pointM1 dan M2 = Center of curveO = center opticR1 dan R2 = Radius of curve

Room of lens

Sumbu utamax x x xM1 F1 O F2 M2

III II I IV

4 1 2 3

M F O F M

Drawing picture

We c a n cha ng e a c o nve x le ns by

X x x x xM1 F1 O F2 M2

+

Dra wing p ic ture

x x x xM1 F1 O F2 M2

SiSo

So = space of object (jarak benda)Si = space of image (jarak bayangan)

Home work

Drawing picture if object on:

1. Room I

2. Room III

3. Focal point

4. Center of curve

Home Work

Complete the table below :

R.Objc R. Image Characteristic

I

II

III

IV

Perbesaran bayangan (M)

Perbesarann bayangan dapat dirumuskan

M = [Si/So] = h’/h

X x x x x O F2 M2

+

Jika benda berada di ruang tigaSifat bayangan :1. Terbalik2. Diperkecil3. nyata

X x x x x O F2 M2

+

Jika benda berada di ruang satuSifat bayangan :1. Tegak2. Diperbesar3. maya

X x x x x O F2 M2

+

Jika benda berada di titik fokusSifat bayangan : ?

X x x x x O F2 M2

+

Jika benda berada di titik pusat kelengkunganSifat bayangan : ?

Untuk m e m p e rm uda h da la m m e lukis ba ya ng a n, le ns a c e kung da p a t d ig a m ba rka n s e p e rti ini

X x x x xM1 F1 O

-

Da la m m e lukis ba ya ng a n d ip e rluka n tig a be rka s s ina r is tim e wa .

X x x x xM1 F1 O

-

Me lukis ba ya ng a n p a da le ns a c e kung

X x x x xM1 F1 O

-

Sifat bayangan :1. Tegak2. Diperkecil3. maya

Me lukis ba ya ng a n p a da le ns a c e kung

X x x x xM1 F1 O

-

Sifat bayangan :1. Tegak2. Diperkecil3. maya

Relation ship between so, si and f

1/So + 1/Si = 1/f

So = jarak bendaSi = jarak bayanganf = jarak fokus

Tugas di rumah !

Lengkapilah tabel berikut :

R.bd R. byg sifat

I

II

III

IV