LIGHT SYIFA RAHMI FADHILA

VIII B

Light is an electromagnetic wave, namely the wave the vibration of which is electrick field and magnetic field.

VIDEO

DEFINITION OF LIGHT

PROPERTIES OF LIGHT

1. Spreading According to Straight Line

2. Has Energy3. Can be Seen4. Radiated in the Form of

radiation 5. Has Spreading Direction

Perpendicular to Vibration Diraction

6. Can Experience Reflection, Refraction, Interference, Diffraction and Polarization

DARK BODYDark body if gets light can be seprated into 3 kinds, namely :

1. Opaque body, namely a dark body that doesn’t continue at all the light it recieve. Exampe : carton, book, wood, and so on

Opaque bodies when lighted by light source then will be formed shadow behind those bodies

Picture

2. Transparent body, namely a dark body that continue a part of light it recieve. Example thin paper.

3. Clear body, namely dark body that continue almost all light it recieve. Example clear glass

Picture

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What’s mean by UMBRA and PENUMBRA ?

Umbra (Core Shadow ) is the region that doesn’t receive light at all so appears dark.

Penumbra is the region that receives a part of light so appears vague.

Law of Light Reflection

a. Incident angle, normal line and reflected ray lie on one flat plane.

b. Incident angle is equal to reflected angle ( i = r ).

Kinds of Light Reflection

Regular Reflecti

on

Irregular Reflectio

n

Light Reflection on Flat Mirror

o Properties that image in flat mirror:

a. Virtual image b. Upright as the bodyc. Same size with the bodyd. Facing perverted with the bodye. Distance of the body to the

mirror is equal to distance of image to the mirror

Light Reflection in Concave Mirror

a. P, namely a center of curvature of the mirror.

b. R, namely a radius of the mirror

c. F, namely focal point (FP=FO)

d. O, namely intersection point of main axis with concave mirror

e. F, namely distance of mirror focus from the point F to point O

f. Main axis is the line that passes through the center of curvature and center point of mirror plane

The magnitude of (f) is half of radius of curvature of the mirror.

Normal line in in the concave mirror’s the line that relates the center point of curvature of mirror P with the ray falling point on the mirror.

f = ½R

Normal Line

Three Particular Rays in the Concave Mirror

1. Incident ray which’s paralles to main axis of the mirror will be reflected passing through the focal point (F)

2. The incident ray passing through the focal point (F) will be reflected parallel to main axis

3. The incident ray passing through center point of curvature of mirror P will be reflected back through that center point of curvature

Properties of Object Image Formed in the Concave Mirror Based on it’s Position

a. Object Lies Infront of P

b. Object Lies Between P and F

c. Object Lies Between F and O

d. Object Lies at the Point

P

e. Object Lies at F

Object distance to the mirror, image distance to the mirror, and focus distance.So the formula:

10 S1

S1

f1

f = ½R

Image magnification’s defined as ratio between heigh (distance) of the object

o

i

o

i

SS

hh

M

objecttheofheighth

imagetheofheighth

ionmagnificat imageM

o

i

Light Reflection in Convex Mirror

Particular rays in the convex mirror :

a. The incident ray parallel to main axid’s reflected seemed comes from focal point of the mirror (F)

b. Incident ray to focal point (F) is reflected parallel t main axis

c. Incident ray to enter of curvature of mirror P is reflected back semmed comes from the center point of curvature (on the same line)

Light Refraction

Light refraction’s light bending that spreads from one medium to another medium of different density.

SNELLIUS LAW

1. Incident ray, refracted ray, and normal line lie on one flat plane and those three intersect at one point.

2. The ratio of projection of incident ray and refracted ray at boundary plane between those two mediums is constant number. The constant number’s defined as index of refraction.

Based on Snellius’s Law, refraction be formulated as follows:

rsinisin

η

o According to Cristian Huygens (1629-1695) a dutch mathematician, physicist, and astronomomer refractive index of matter’s defined as follows.

o Refractive index of a matter’s ratio between light velocity in vacuum to light velocity in that matter.

nCC

η

mediuminvelociylightC

m/s10x3isvacuuminvelocitylightC

mediumofindexrefractiveη

n

8

In wave there’s relationship between veocity, wave length and frequency, namely relationship

λ.fC

nCC

ηnn f.λ

f.λ

nλλ

η

mediuminwavelenghtlightλ

airinwavelenghtlightλ

mediumofindexrefractionη

n

Optical Things That Can Make Light Refraction

1. Planparallel Glass is the tick glass the surface of which’s flat.

and

i = angle of incident ray (air to planparallel glass)r = angle of refracted ray (air to planparallel

glass)i’ = angle of incident ray (planparallel glass to air)r’ = angle of refracted ray (planparallel glass to

air)

i = r’ r = i’

2.Prism3.Lensa. Convex Lensb.Concave Lens

Power Of Lens

P = power of lensf = focus distance

f1

P