Mirror

By :Aries Triwidajati Soenoko

SMP Negeri 2 Cileunyi

Basic Competence

Investigate the characteristic of light and the relation with mirror and lens

Learning Objectives

After this lesson, student are able to :1. Drawing of an image through a ruler in

the mirror

2. Mention the characteristics of an image in the mirror

3. Calculate focus, object, image, and magnification positions.

Concave Mirror

Characteristic of concave mirror1. Concave mirror is part of the inner surface

of a hollow sphere2. Concave mirror product converge ray3. CM in daily life is used to collect ray, such as

: solar panel,

Principal axisM F O

Reflection of light in CM

Part of CM

M is geometric center (pusat lingkaran) R is the sphere radius (jari-jari) A is the center of mirror (pusat cermin) MA is the principal axis (sumbu utama) F is the focal point of the mirror (focus) FA is the focal lengt (jarak focus) The focal length is half the distance

between the mirror and the center of curvature M.

Sumbu utamaM F O

Real image

Paralel ray of the sun aor other object are reflected from a concave mirror at the focal point (F) of mirror

The focal point become bright on the paper, it is called image of the sun

An image is real image if rays actualy converge and pass trough the image

A real image can be seen on a piece of paper or screen.

Virtual image

A virtual image cannot be seen on a piece of paper or screen because, light rays do noot converge at virtual image.

Image of plan mirror is example of virtual image.

Drawing image on Concave mirror

Using three kind of rays1. The ray parallel of principle axis is

reflected through the focal point (F)2. The ray passing trough F is reflected

parallel to the principle axis3. The ray passing trough the center of

curvature C is reflected along its same path through C

Sumbu utamaM F O

Three kind of rays

Sumbu utamaM F O

Making image

Inverted, virtual, smaller

Sumbu utamaM F O

Inverted, virtual, bigger

Sumbu utamaM F O

Upright, virtual, bigger

Sumbu utamaM F O

Tidak terbentuk bayangan

Sumbu utamaM F O

Reverse, virtual, equal

Principle axisM F O

Making image

Bayangan diperkecil, terbalik dan nyata

III II I IV

Sumbu utamaM F O

Making image

Bayangan diperkecil, terbalik dan nyata

Sumbu utamaM F O

Bayangan diperbesar, terbalik dan nyata

Sumbu utamaM F O

Bayangan diperbesar, tegak dan maya

RESUME

ObjectRoom

ImageRoom

Characteristic of image

I IV Upright, virtual, bigger

II III Reverse, real, bigger

III II Reverse, real, smaller

IV I Upright, virtual, smaller

Go to menu Go to resume

Convex MirrorCharacteristic of convex mirror1. Convex mirror is part of the outer surface of a

hollow sphere2. Convex mirror product diverge ray3. Convex mirror does not form real image4. Convex mirror in daily life is used in car, and its

is used in stores to observe shoppers. 5. Focal point (f) is placed behind mirror (the focal

length is a negative number)

Sumbu utamaA F M

Principle axis

A F M

Three kind of light

Sumbu utamaA F M

Making image in convex mirror

Three kind of ray1. The ray parallel to the principal axis is

reflected as if it is from focal point (f)2. The ray to focal point is reflected parallel

to the principal axis3. The ray to the center of curvature M is

reflected along its same path through M

Sumbu utamaA F M

Making image in convex mirror

Sumbu utamaA F M

Sumbu utamaA F M

An equation can also be used to located the image and find its size. The focal length (f) the distance of the object from the mirror (S0) and the distance of the image from the mirror (S1) are related by the mirror equation :

10

111

SSf

The ratio of the size of the image (hi) to the size of the object (h0) is called the magnification (m). The magnification is related to the distances to the mirror by equation :

00 S

S

h

hm ii

If Si and S0 positive, the both m and hi are negative. This means that the image is inverted.

Resume

f always negative (-) Convex mirror always form virtual image,

smaller and upright The object always on the 4th room

Characteristics of Focus of a Concave and a Convex Mirror

 

Review1. A concave mirror has a radius of curvature of 60

cm. Calculate the image position and magnification of an object placed in front of the mirror at distances of (a) 90 cm and (b) 20 cm. (c) Draw ray diagrams to obtain the image in each case.

2. Calculate the image position and magnification for an object placed (a) 20 cm and (b) 60 cm in front of a convex mirror of focal length 40 cm. (c) Use ray diagrams to locate image positions corresponding to the object positions in (a) and (b).

TIDAK ADA KATA SULIT BAGI KALIAN YANG INGIN MAJU

Good Luck

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