light scattering and dispersion

7/30/2019 light scattering and dispersion

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7.3

Penyebaran

cahaya


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Penyebaran cahaya

Penyebaran cahaya ialah proses cahaya

putih dipecahkan kepada juzuk

juzukwarnanya yang disebut spektrum apabila

prisma.


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Penyebaran cahaya

Sepktrum terdiri daripada tujuh warnadalam tertib ini: merah, jingga, kuning,

hijau, biru, indigo dan ungu.

Penyebaran cahaya berlaku kerana setiap

juzuk warna bergerak pada kelajuan yang

berlainan melalui prisma.


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Penyebaran cahaya

Oleh sebab itu, cahaya

cahaya berwarnadibiaskan pada sudut yang berbeza.

Cahaya ungu banyak dibiaskan oleh prisma

kaca berbanding dengan cahaya merah yang

mempunyai panjang gelombang yang lebih

panjang. Hal ini demikian, kerana cahaya

ungu bergerak dengan halaju yang paling

perlahan.


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Light Dispersion

The seven spectral colours in order of

increasing frequency are red, orange, yellow,

green, blue, indigo and violet. (ROY G BIV)


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Light Dispersion

The different colours in the spectrum are

actually:

Lights waves of different wavelengths. Red

light has the longest wavelength (panjang

gelombang), violet the shortest.

The shortest wavelengths are refracted more

than the longer wavelengths because of thedifferent speeds at which different

wavelengths pass through the refracting

medium.


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Natural phenomenon of light dispersion


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A rainbow can be seen during a drizzle in

the morning or afternoon when sunlight

shines on the raindrops.

A person can see a rainbow when his

back is behind the sun.


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A raindrop acts as aprism.

The Formation of Rainbow

A rainbow is formedwhen sunlight passes

through raindrops.

The sunlight is refracted and dispersed into its

colour constituents


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7.4

Light scattering (penyerakancahaya)


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Light scattering

Is the reflection of light in different directions bythe air molecules or by the particles in the

atmosphere.

The atmosphere contains gas molecules, vapourand dust.

When the sunlight is blocked by the gas

molecules and the tiny particles, it will be

scattered.


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Blue sky
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Formation of blue sky

At noon, sunlight passes through a thinatmosphere layer.

Red and orange lights which have long

wavelength pass through the atmospheredirectly.

Blue light which has a short wavelength is

scattered more in all directions.

This cause the sky to appear blue.


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Red sky during sunset
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Formation of red sky

At sunset, sunlight passes through a thicker

atmosphere layer.

Red and orange lights with long wavelengths

pass through the atmosphere. Both are less

scattered.

Consequently, red and orange lights can be

observed.

This cause the sky to appear red or orange at

sunset.


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EXERCISE SPS

7.10 Inquiry Experiment (pg 114)

7.11 Inquiry Experiment (pg 116)

7.13 Discussion Activity (pg 118)


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Observation :

7.10 Inquiry Experiment

Spectrum colours

Red

Orange

Yellow

Green

Blue

Indigo

Violet


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1. How does light dispersion occur?

Analysis :

The coloured light rays in white light move at

different speeds through the prism. Thus,

the coloured light rays are refracted atdifferent angles.


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2. What coloured light is refracteda) The most?

b) The least?

Analysis :

Violet light

Red light


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3. Give an inference for your answer in (2)

Analysis :

Violet light moves the slowest whereas red

light moves the faster.

4. What processes occur when a beam of light

passes through a prism?

Dispersion and refraction


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light scattering and dispersion

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