Download - Light tugas fisika
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 1/48
• What do you feel if there is no light?
• Can you see an object around you?
Let’s look next slide
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 2/48
pelindung orang-orang yang beriman. Dia
mengeluarkan mereka dari kegelapan menuju
cahaya.(QS 2:257)
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 4/48
Indicators
You are able to :
• Design experiment to study about the
direction of light travel. – By using OHP or candle to make shadow(s)
• Observ form of shadow, to explain light
characteristic(s,k)
• Make deffer betwen shadow and image
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 6/48
• Light spread out from light sources toall direction.
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 7/48
Light source is dot
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 8/48
Source of light like dot
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 9/48
CONCLUSION
• When something block a light, wewill see a shadow.
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 10/48
Shadow (bayang-bayang)
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 11/48
CONCLUSION• A wayang playing and making shadow
are of phenomena suggest that lighttravels in straight lines.
• Light travels in straight line in vacuum or uniform medium.
• In drawing illustrating the paths of
straight line it is use light rays
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 12/48
CONCLUSION• Seeing is actually a rather passive
activity.
• What you see depends on the light thatenters your eyes and not on somemysterious rays that leave them.
• In fact, light passing through clean air is
invisible.
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 13/48
CARACTERISTIC OF LIGHT
1. Have velocity 300.000.000 m/s
2. Part of solar system spectrum
3. An electromagnetic wave
4. Travels in straight line
5. Can be reflection6. Can be refraction
7. Can be dispersion
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 14/48
We are going to learn three kind
of LIGHT
•Reflection
•Refraction
•Dispersion
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 15/48
LIGHT
REFLECTION REFRACTION DISPERSION
PLANE MIRROR CONCAVE MIRROR CONVEEX MIRROR CORVERGING LENS DIVERGING LENS
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 16/48
Shadow and Image
• Shadow (bayang-bayang) is dark area
on the back of object
• Image (bayangan) is light area, it is the
area that the light come together
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 17/48
Moon eclipse diagram
Umbra
Penumbra
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 19/48
Shadow can devided in two part
• Umbra : The darkest region is where all of
the shadow overlap.
• Penumbra : The darkest region is whereonly some of the shadow overlap.
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 20/48
REFLECTION OF LIGHT
Diffuse reflection
Regular reflection
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 21/48
Activity
• Do activity page 265
• To investigation the relation between te
angle of incidence and the angle of reflection
• To find out the characteristic of mirror
plane image
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 22/48
The reflection of light on a plane mirror
Incidence ray normal line reflected ray
x x
The incidence angle the reflected angle
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 23/48
THE LAW OF REFLECTION
• The incident ray, the reflected ray and thenormal surface at the point of incident all lieon the same plane.
• The angle of incidence is equal to the angleof reflection.
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 24/48
Pemantulan pada Cermin Datar
Sifat bayangan Cermin datar•
Sama besar dengan bendanya• Jarak bayangan = jarak benda
• Posisi bayangan tertukar
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 25/48
Pembentukan bayangan pada cermin datar
Jarak benda = jarak bayangan
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 26/48
Susunan dua buah cermin datar
• Susunan dua buah cermin datar akan
menghasilkan jumlah bayangan yang lebih
dari satu, hal tersebut tergantung besarsudut antara dua cermin datar tersebut.
• Bagaimanakah hubungan antara jumlahbayangan dan besarnya sudut ?
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 27/48
Sudut dua cermin 90o
Hitung banyaknya bayangan yang terbentuk ?
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 28/48
Pematulan pada Cermin cekung
Sifat-sifat Cermin Cekung
1.Permukaan cermin melengkung ke dalam
2.Mengumpulkan berkas sinar
3.Digunakan pada lampu senter, lampu mobil
dll.
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 29/48
PEMBENTUKAN BAYANGAN PADA CERMIN
CEKUNG
Tiga berkas sinar istimewa
1. Sinar datang sejajar sumbu utama
dipantulkan menuju titik fokus (F)2. Sinar datang melelui titik fokus (F)
dipantulkan sejajar sumbu utama
3. Sinar datang yang melalui pusatkelengkungan, dipantulkan kembalimelalui pusat kelengkungan (M)
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 30/48
Sumbu utamaM F O
TIGA BERKAS SINAR ISTIMEWA
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 31/48
Sumbu utamaM F O
TIGA BERKAS SINAR ISTIMEWA
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 32/48
Sumbu utamaM F O
PEMBENTUKAN BAYANGAN PADA CERMIN CEKUNG
Bayangan diperkecil, terbalik dan nyata
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 33/48
Sumbu utamaM F O
Bayangan diperbesar, terbalik dan nyata
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 34/48
Sumbu utamaM F O
Bayangan diperbesar, tegak dan maya
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 35/48
Sumbu utamaM F O
Tidak terbentuk bayangan
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 36/48
Sumbu utamaM F O
Bayangan sama besar, terbalik dan nyata
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 37/48
An equation can also be used to located the
image and find its size. The focal length (f) thedistance of the object from the mirror (S0) and
the distance of the image from the mirror (S1)
are related by the mirror equation :
10
111SS f
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 38/48
The ratio of the size of the image (h1) to the size of
the object (h0) is called the magnification (m). Themagnification is related to the distances to the mirror
by equation :
0
1
0
1
S
S
h
hm
If S1 and S0 positive, the both m and h1 are
negative. This means that the image is
inverted.
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 39/48
PEMBENTUKAN BAYANGAN PADA CERMIN CEMBUNG
Tiga berkas sinar istimewa
1. Sinar datang sejajar sumbu utama dipantulkan
seolah-olah berasal dari titik fokus (F)2. Sinar datang menuju titik fokus (F) dipantulkan
sejajar sumbu utama
3. Sinar datang menuju pusat kelengkungan
cermin, dipantulkan kembali seolah-olah berasal
dari pusat kelengkungan (M)
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 40/48
TIGA BERKAS SINAR ISTIMEWA
Sumbu utamaF O F
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 41/48
TIGA BERKAS SINAR ISTIMEWA
Sumbu utamaF O F
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 42/48
Sumbu utamaM O F
PEMBENTUKAN BAYANGAN PADA CERMIN CEMBUNG
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 43/48
Sumbu utamaM O F
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 44/48
Sumbu utamaM O F
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 45/48
EXERCISE :
1. An object is 15 cm from a spherical
concave mirror having a 20 cm radius.
Locate the image by means of :a. a ray diagram
b. the mirror equation
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 46/48
Solution :
a.
f f OM 10
20
10
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 47/48
b. Known : R = 20 cm
f = ½ R = ½ x 20 = 10 cm
S0 = 15 cmAsk : S1……………………..?
Solution :
1/S1 = 1/f - 1/S0
= 1/10 – 1/15 = 3/30 – 2/30
= 1/30
S1 = 30 cm
8/2/2019 Light tugas fisika
http://slidepdf.com/reader/full/light-tugas-fisika 48/48
2. An object 15 cm in height is 12 cm from 1 sphericalmirror having a 12 cm radius. Locate the image by
means of :a. a ray diagram
b. the mirror equation
c. what is the height of the image
3. An object is located so that a virtual image is formed24 cm behind a concave mirror that has an 8 cm focallength.
a. calculate the object distance
b. if the image is 12 cm, what is the size of theobject?