6.2 Total Internal Reflection (Vol 1)

Physics
Chapter 6 Light and Optics

Cahaya dan Optik

6.2 Total Internal
Reflection

Pantulan Dalam Penuh

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

6.2 Total Internal Reflection

The reflected images on the boundary
of water and air can be seen.
Why does this happen?
This phenomenon is known as total

internal reflection of light.

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Suppose it refracted
out from water.

Image formed on the
boundary of water.

But the light reflected So we see the images on the boundary
back into the water. of water due to total internal reflection

like what happened in the mirror.

3 by CHU MP

Total internal reflection only occurs when light travels from a CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

medium of high optical density to a medium of low optical density.

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

The phenomenon of total internal reflection happens when the angle of

incidence larger than the critical angle, c.

Critical angle, c is the angle of incidence in the medium of high optical

density when the angle of refraction in the medium of lower optical density is

equals to 90º. when the angle of

refraction is equals to 90º.

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Refracted CHAPTER 6 LIGHT AND OPTICS
angle is 90º. 6.2 TOTAL INTERNAL REFLECTION

sin 90o = 1

2 = sin 90o ∴ = 1
1 sin Ɵ
Air medium, sin
n1 = 1.
Ɵ as critical angle, c when
refracted angle = 90o

when the angle of
refraction is 90º.

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Incident angle is When light ray going CHAPTER 6 LIGHT AND OPTICS
less than critical to travels from a 6.2 TOTAL INTERNAL REFLECTION
medium of high
angle Refracted away
density to a medium
i<c of low density. from normal line

Incident angle is When light ray going (refraction)
same as critical to travels from a
medium of high Refracted with
angle
density to a medium refracted angle
i=c of low density. r = 90o

Incident angle is When light ray going Total internal
greater than to travels from a
critical angle medium of high reflection occurs.

i>c density to a medium
of low density.

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For example, if the refractive CHAPTER 6 LIGHT AND OPTICS
index of diamond is 2.42, find c. 6.2 TOTAL INTERNAL REFLECTION

∴ = 1 Critical angle, c

sin Critical angle for a medium depends
on the optical density of the medium.
8 The higher the refractive index of a
medium, the smaller the critical
angle of the medium. Meaning that
total internal reflection can occur
many times inside the medium.

CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Natural Phenomena that Involve Total Internal Reflection

Pembiasan (refraction) dan Formation of rainbow
penyebaran (dispersion)
Pantulan dalam
penuh (total

internal reflection)

Matahari mesti berada
di sebelah/belakang
kita supaya pelangi
terbentuk di depan
kita.

CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Natural Phenomena that Involve Total Internal Reflection

Mirage Logamaya

Hot and bright day

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Natural Phenomena that Involve Total Internal Reflection

Hot and bright day Mirage Logamaya

Refraction (cahaya
terbias) occurs.

Hotter layer, lower optical Total internal reflection occurs,
density. because incident angle larger

11 than critical angle, c,.

CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Natural Phenomena that Involve Total Internal Reflection

At night Mirage Logamaya

Total internal
reflection occurs.

Air layer above sea
water is cooler.

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Applications of Total Internal Reflection in Daily Life
Prism periscope

Total internal
reflection.

Total internal
reflection.

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Two types of periscope

Apply reflection Apply total
by using mirror internal reflection
reflection by using

prism (glass)

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Applications of Total Internal Reflection in Daily Life

Optical fibre

CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Applications of Total Internal Reflection in Daily Life
Optical fibre

Widely used in the fields of
telecommunication and
medicine.
Made from pure glass or
plastic fibres.

Inner core which has a high
refractive index is surrounded
by a layer of cladding with a low
refractive index.

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Applications of Total Internal Reflection in Daily Life
Cat’s eye reflector

Light rays from car headlights enter the
reflector and experience total internal
reflection on the back surface of the reflector.

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CHAPTER 6 LIGHT AND OPTICS
6.2 TOTAL INTERNAL REFLECTION

Applications of Total Internal Reflection in Daily Life
Diamond and its sparkle

The critical angle for a diamond-to-air surface is
very small only 24.4º, and so when light enters a
diamond, it has trouble getting back out, sparkle
more than other materials.

Total internal
reflection
occurs.

Total internal
18 reflection occurs.

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