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Total Internal Reflection and Critical Angle

Vedio

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Normal

Ray box

Semi-circular block glassi

r

i = 42o

r = 90o

i = Critical angle, c = 42o

Refractive index, n = sin Vsin m

n = sin 90 = 1sin c sin c

n = 1/(sin 42o) =

Tangent

when r = 90o

What happen if i is biggerthan c?

The light is reflected internalat the surface in a medium(glass).

Its known as Total Internal

Reflection

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Normal

Ray boxTangent

State two conditions for total internal reflection could occur.

ci

Glass: high

density

Air: low

density

i) Light ray passes from a denser medium to a less dense medium

ii) The angle of incidence (in the denser medium) is greater than the

critical angle.

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The shape of glasses:

Glass Block

Semi-circularGlass Prism Block

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Prism: Observe the changes of the ray when the angle of incidence ray

in prism is increased.

Vedio

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Figure a Figure a

PQ

PQ

2. Determine the critical angle of prism which are used.

1. How do you explain the condition of the light which passes in theprism?

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Natural Phenomenon Involving Total Internal Reflection

1. Mirage (Logamaya / fatamorgana)

Object(cloud)

Warm air layer

(low density)

Cool air layer

(high density)

Image(cloud)

The ray from objectis bent (refracted)

Observer

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Lagu: Logamaya (Amok)

Logamaya yang temberang

Salah paham menyesatkanSinar cahya dari awan

Dibiaskan dan dipantulkan

Dari lapisan udara kesejukan

Ke lapisan udara kepanasanCahaya dibias dan dipantul dalam (penuh)

Medium yang sama

Ke mata perhati

Yang kelihatan imej awan-awan

Bagai kolam ikan di tengah jalanan

Aku manusia

Yea, yeah.

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2. Rainbow

Discuss;

How does it occur

The phenomenon of light that is involved

Why it is being colourful?

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3. Diamond

Discuss;

i) Refractive index (low or high)

ii) Phenomenon of light

iii) The effect when being exposed to light

Lihat intan dari arang dari lumpur terpendam, lama himpitan kepanasan kini barangbernilai.

Mampukah dirimu jadi seperti itu, atau dirimu hancur lebur.

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The Application of Total Internal Reflection

1. Periscope

Object

Image

Prism

Prism

Observer

Discuss;

The use of the device

The main components and its

functions

The arrangement of prisms

How does it work

The phenomenon of light

Characteristics of image

The advantage of prisms

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2. Binocular

Discuss;

The use of the device

The main components and its

functions

The arrangement of prisms

How does it work

The phenomenon of light

Characteristics of image

The advantage of prisms

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3. Bicycle and Car Reflector and Cat Eyes

Discuss;

The shape of prism

How does it work

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4. Optical Fibre

Discuss;

The use of the device

The main components

How does it work

The phenomenon of light