LIGHT

By:

Kurniawati Ahmida

09330063 / 5B

OBJECTIVIES OF LEARNING

Student can to explain the properties of light Student can to explain the law of light

reflection, draw image formation on the flat mirror, concave mirror, and convex mirror

Student can to explain the law of light refraction, draw image formation in concave lens, and convex lens and explain the image properties in concave lens and convex lens, calculate the power of lens

LIGHT?

Light is an elektromagnetic wave, namely the wave the vibration of which is electric field and magnetic field. Different with sound, light can spread without medium, so light can spread in vacuum. That’s why, sunlight can arrive to the earth eventhough between the sun and the earth is found vacuum space

While several properties of light among other are:

• Spreading according to straigt Line• Has energy• Can be seen• Radiated in the from of radiation• Has spreading direction perpendicular to

vibration direction• Can experience reflection, refraction, inter

ference, diffraction, and polaritation

LIGHT REFLECTION

Law of Light Reflection:a. Incide angle, normal line and

reflected ray lie on one flat planeb. Incident angle is equal to reflected

angle (i = r)

mirror

Incident angle

Normal line

Reflected ray lie

i = sudut datang

r = sudut pantul

The Kinds of Light Reflection

Specular Reflection Diffuse Reflection

Light Reflection on flat Mirror

a. Virtual imageb. 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

1. Incident ray which is paralles to main axis ef 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.

Formation of a shadow on the concave mirror

Concave mirror equation

or

An object is placed 20 cm infront of a concave mirror with radius of curvature of 30 cm. What is the distance of image to the mirror and the image magnification ?

Solution:Given: S = 20 cm

R = 30 cmAsked: S’ and M ?Answer:

So, the image distance is 60 cm in front of mirror

So, the image magnification is 3 time

Light Reflection in Convex Mirror

1. The incident ray parallel to main axis is reflected seemed comes from focal of the mirror (F).

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

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

Convex Mirror Equation

or

Light Refraction

Light refraction is phenomenon of bending of light that spreads from one medium to another medium which density are different.

Law of refraction: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 refracted ray at boundary plane between those two medium is constant number is defined as index of refraction.

Convex Lense

1. Incident ray parallel to main axis is refracted through active focus F1.

2. Incident ray through positive focal point F2 is refracted parallel to main axis.

3. Incident ray through lens center point O is continued without experiencing refraction.

Concave Lens

1. Incident ray Parallel to main axis is refracted seemed comes from active focal point F1.

2. Incident ray seemed goes to passive focal point F2 is refracted parallel to main axis.

3. Incident that goes to optic center point of lens is continued without refraction.

An object is put 20 cm infront of a convex lens. If focus distance of the lens is 15 cm, what is:a. Image distance from the lensb. Image magnification c. Properties of image

Solution:Given: S = 20 cm

f = 15 cmAsked: a. S’..?

b. M..?c. Properties of image..?

Answer:

So, image distance from the lens is 60 cm behind the lens

So, image magnification is 3 times

Properties of image is real, inversed enlarged.