understanding refraction of light

7/29/2019 Understanding Refraction of Light

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Lets Do Some Activity


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WATER & STRAW


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5.2 Understanding

Refraction of Light


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Refraction

Is due to a change in the speed of

light as it passes from one medium

to another.

Referred to as bending of light.


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Bending of light


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Reflection?


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Reflection

The angle ofincidence

=

The angle ofreflection


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New Verb

Incident Ray

The ray in the first medium

Angle of Incident, I

The angle between the incidentray and the normal.


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New Verb

Refracted Ray

The light ray in the second medium

Angle of Refracted

The angle between the refracted ray andthe normal.


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How the light ray

moved in the twodifferent medium?


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Incident RayNormal

Refracted Ray

i

r


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Bending of light can happen in two

different situation :

Less dense medium to

densermedium

Densermedium to less

dense medium

Figure A Figure B


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FST = Fast to Slow, Towards Normal

If a ray of light passes across the boundaryfrom a material in which it travels fast into a

material in which travels slower, then the light

ray will bend towards the normal line

SFA = Slow to Fast, Away From

Normal

If a ray of light passes across the boundary

from a material in which it travels slow into a

material in which travels faster, then the light

ray will bend away from the normal line.


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Refractive Index

Refractive index, n

The speed of light will decreased whenit enters an optically densermedium.

Increase when it enters an optically less

dense medium.

iumhtInTheMedSpeedOfLigairhtInVacumSpeedOfLign /


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Refractive Index Table

MEDIUM REFRACTIVE INDEX,n

Vacuum 1.00

Air 1.0003 = 1.00Water 1.33

Ethanol 1.36

Glycerin 1.47Crown Glass 1.52

Diamond 2.42


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Laws of Refraction( SNELLS LAW)

i. The incident ray, the refracted ray and

the normal all lie in the same plane.

ii. The ratio of the sine of the angle of

incidence ( sin i ) to the of the angle of

refraction ( sin r) is a constant

mediumr

vacuumin

sin

sin


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Real Depth & ApparentDepth

Real depth : The distance between the

water surface and the object. (D)

Apparent depth: The distance between

the water surface and the image. (D)

',

,Re

DpthApparentDe

DalDepthn


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DD

image

object


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LUCKY CHARMEDNUMBER ZERO


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F lash Mov ie
http://localhost/var/www/apps/conversion/tmp/scratch_8/refraction.swf


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QUESTION1

If the speed of light in vacuum is3x 108m s-1 and the refractive

index of glass is 1.5.

Calculate the speed of light inglass.


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ANSWER

iumhtInTheMedSpeedOfLig

airhtInVacumSpeedOfLign

/

v

ms18

1035.1

18100.2

msV


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QUESTION2

A light ray travels from the medium air tomedium glass. If the angle of incident is andthe refractive index of glass is 1.5.Calculate the angle of refraction.


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ANSWER

n

isinsin

5.1

30sinsin

r

33.0sin r

47.19r


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QUESTION3Refractive index of ice is 1.31 and

the speed of light in vacuum is 3 x

108 m s-1.

Calculate the speed of light in ice.


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ANSWER

iumhtInTheMedSpeedOfLig

airhtInVacumSpeedOfLign

/

v

ms 1810331.1

181029.2

msV


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QUESTION4

A light ray travels from the ice medium to the airmedium. If the speed of light in vacuum is 3 x108 m s-1 and the refractive index of glass is1.31. Calculate the angle of refraction,


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ANSWER

rn

sin

sin

15sin)31.1(sin

339.0sin

8.19


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QUESTION5

A light ray travels from the liquid medium tothe air medium. If the angle of incident is 45degree and the angle of refraction is 60degree. Calculate the refractive index.


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ANSWER

mediumr

vacuumin

sin

sin

45sin

60sinn

22.1n


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QUESTION6

A light ray travels from the glass medium tothe air medium. If the angle of incident is 25degree and the refractive index of glass is1.5. Calculate the angle of refraction.


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ANSWER

r

in

sin

sin

25sin5.1sin i

34.39i


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Cut & Paste Puzzle

Have you understand about the less

dense medium and denser medium?

Now, show how the light rays travel:-

Less dense medium to denser medium.

Denser medium to less dense medium.

understanding refraction of light

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