tugas fisika (annisa x.6.06)

7/29/2019 Tugas Fisika (Annisa x.6.06)

1/5

TUGAS FISIKA

TOTAL INTERNAL REFLECTION

OLEH :

ANNISA FIRDAUZI / X.6 / 06

PEMERINTAH KOTA MALANG

DINAS PENDIDIKAN

SEKOLAH MENENGAH ATAS NEGERI 1 MALANG

Jalan Tugu Utara No. 1, Telp. (0341) 366454, Fax. (0341) 329487 MalangWebsite : http://www.sman1-mlg.sch.id

Email : [email protected]
http://www.sman1-mlg.sch.id/mailto:[email protected]://www.sman1-mlg.sch.id/mailto:[email protected]


2/5

Total internal reflection

Total internal reflection is a phenomenon that happens when a propagating wave strikes a

medium boundary at an angle larger than a particularcritical angle with respect to the normal

to the surface. If the refractive index is lower on the other side of the boundary and the

incident angle is greater than the critical angle, the wave cannot pass through and is entirely

reflected. The critical angle is the angle of incidence above which the total internal

reflectance occurs. This is particularly common as an optical phenomenon, where light waves

are involved, but it occurs with many types of waves, such as electromagnetic waves in

general orsound waves.

When a wave crosses a boundary between materials with different kinds of refractive indices,

the wave will be partially refracted at the boundary surface, and partially reflected. However,

if the angle of incidence is greater (i.e. the direction of propagation or ray is closer to being

parallel to the boundary) than the critical angle the angle of incidence at which light is

refracted such that it travels along the boundary then the wave will not cross the boundaryand instead be totally reflected back internally. This can only occur where the wave travels

from a medium with a higher [n1=higher refractive index] to one with a lower refractive index

[n2=lower refractive index]. For example, it will occur with light when passing from glass to

air, but not when passing from air to glass.

Optical description

Total internal reflection of light can be demonstrated using a semi-circular block of glass or

plastic. A "ray box" shines a narrow beam of light (a "ray") onto the glass. The semi-circular

shape ensures that a ray pointing towards the centre of the flat face will hit the curved surface

at a right angle; this will prevent refraction at the air/glass boundary of the curved surface. Atthe glass/air boundary of the flat surface, what happens will depend on the angle. Where c is

the critical angle measurement which is caused by the sun or a light source (measured

normal to the surface):

If c, the entire ray reflects from the boundary. None passes through.This is called total internal reflection.

This physical property makes optical fibers useful and prismaticbinoculars possible. It is alsowhat gives diamonds their distinctive sparkle, as diamond has an unusually high refractive

index.

Critical angle

The critical angle is the angle of incidence above which total internal reflection occurs. The

angle of incidence is measured with respect to the normal at the refractive boundary (see

diagram illustrating Snell's law). Consider a light ray passing from glass into air. The light

emanating from the interface is bent towards the glass. When the incident angle is increased

sufficiently, the transmitted angle (in air) reaches 90 degrees. It is at this point no light istransmitted into air. The critical angle is given by Snell's law,
http://en.wikipedia.org/wiki/Wavehttp://g/Total_internal_reflection.htm#Critical_anglehttp://en.wikipedia.org/wiki/Normal_(geometry)http://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/wiki/Reflection_(physics)http://en.wikipedia.org/wiki/Angle_of_incidencehttp://en.wikipedia.org/wiki/Optical_phenomenonhttp://en.wikipedia.org/wiki/Electromagnetic_waveshttp://en.wikipedia.org/wiki/Sound_waveshttp://en.wikipedia.org/wiki/Refractionhttp://en.wikipedia.org/wiki/Earth's_atmospherehttp://en.wikipedia.org/wiki/Ray_(optics)http://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Binocularshttp://en.wikipedia.org/wiki/Normal_(geometry)http://en.wikipedia.org/wiki/Snell's_lawhttp://en.wikipedia.org/wiki/Wavehttp://g/Total_internal_reflection.htm#Critical_anglehttp://en.wikipedia.org/wiki/Normal_(geometry)http://en.wikipedia.org/wiki/Refractive_indexhttp://en.wikipedia.org/wiki/Reflection_(physics)http://en.wikipedia.org/wiki/Angle_of_incidencehttp://en.wikipedia.org/wiki/Optical_phenomenonhttp://en.wikipedia.org/wiki/Electromagnetic_waveshttp://en.wikipedia.org/wiki/Sound_waveshttp://en.wikipedia.org/wiki/Refractionhttp://en.wikipedia.org/wiki/Earth's_atmospherehttp://en.wikipedia.org/wiki/Ray_(optics)http://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Binocularshttp://en.wikipedia.org/wiki/Normal_(geometry)http://en.wikipedia.org/wiki/Snell's_law


3/5

. Rearranging Snell's Law, we get incidence

To find the critical angle, we find the value for when 90 and thus. The resulting value of is equal to the critical angle . Now, we can

solve for , and we get the equation for the critical angle:

If the incident ray is precisely at the critical angle,the refracted ray is tangent to the boundary at the point of incidence. If forexample, visible light were traveling through acrylic glass (with an index ofrefraction of 1.50) into air (with an index of refraction of 1.00), the calculation

would give the critical angle for light from acrylic into air, which is

.

Light incident on the border with an angle less than 41.8 would be partiallytransmitted, while light incident on the border at larger angles with respect to

normal would be totally internally reflected. If the fraction is greaterthan 1, then arcsine is not definedmeaning that total internal reflectiondoes not occur even at very shallow or grazing incident angles.

So the critical angle is only defined when is less than 1.

Refraction of light at the interface between two media, including total internalreflection.A special name is given to the angle of incidence that produces anangle of refraction of 90. It is called the critical angle.

Applications

Total internal reflection is the operating principle ofoptical fibers, which

are used in endoscopes and telecommunications.
http://en.wikipedia.org/wiki/Tangenthttp://en.wikipedia.org/wiki/Poly(methyl_methacrylate)http://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Endoscopehttp://en.wikipedia.org/wiki/File:RefractionReflextion.svghttp://en.wikipedia.org/wiki/Tangenthttp://en.wikipedia.org/wiki/Poly(methyl_methacrylate)http://en.wikipedia.org/wiki/Optical_fiberhttp://en.wikipedia.org/wiki/Endoscope


4/5

Total internal reflection is the operating principle of automotive rainsensors, which control automatic windscreen/windshield wipers.

Another application of total internal reflection is the spatial filtering oflight.[2]

Prismatic binoculars use the principle of total internal reflections to get a

very clear image. Some multi-touch screens use frustrated total internal reflection in

combination with a camera and appropriate software to pick up multipletargets.

Gonioscopy employs total internal reflection to view the anatomical angleformed between the eye's cornea and iris.

A gait analysis instrument, CatWalk XT, uses frustrated total internalreflection in combination with a high speed camera to capture and analyzefootprints of laboratory rodents.

Optical fingerprinting devices use frustrated total internal reflection inorder to record an image of a person's fingerprint without the use of ink.

SureFire's high-performance flashlight lenses use total internal reflectionto gather more light from an LED than a conventional reflector could. ATotal internal reflection fluorescence microscope uses the evanescent

wave produced by TIR to excite fluorophores close to a surface. This isuseful for the study of surface properties of biological samples.

Examples in everyday life

Total internal reflection can be observed while swimming, when one opens one's eyes

just under the water's surface. If the water is calm, its surface appears mirror-like.

One can demonstrate total internal reflection by filling a sink or bath with water,

taking a glass tumbler, and placing it upside-down over the plug hole (with the

tumbler completely filled with water). While water remains both in the upturnedtumbler and in the sink surrounding it, the plug hole and plug are visible since the

angle of refraction between glass and water is not greater than the critical angle. If the

drain is opened and the tumbler is kept in position over the hole, the water in the

tumbler drains out leaving the glass filled with air, and this then acts as the plug.

Viewing this from above, the tumbler now appears mirrored because light reflects off

the air/glass interface.

Mirror like effect

Another common example of total internal reflection is a critically cut diamond. This

is what gives it maximum sparkle.
http://en.wikipedia.org/wiki/Rain_sensor#Automotive_sensorshttp://en.wikipedia.org/wiki/Rain_sensor#Automotive_sensorshttp://en.wikipedia.org/wiki/Windscreen_wiper#Historyhttp://g/Total_internal_reflection.htm#cite_note-2http://en.wikipedia.org/wiki/Binoculars#Prism_binocularshttp://en.wikipedia.org/wiki/Multi-touchhttp://en.wikipedia.org/wiki/Gonioscopyhttp://en.wikipedia.org/wiki/Corneahttp://en.wikipedia.org/wiki/Iris_(anatomy)http://en.wikipedia.org/wiki/Gait_analysishttp://en.wikipedia.org/wiki/Fingerprinthttp://en.wikipedia.org/wiki/Light-emitting_diodehttp://en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscopehttp://en.wikipedia.org/wiki/Rain_sensor#Automotive_sensorshttp://en.wikipedia.org/wiki/Rain_sensor#Automotive_sensorshttp://en.wikipedia.org/wiki/Windscreen_wiper#Historyhttp://g/Total_internal_reflection.htm#cite_note-2http://en.wikipedia.org/wiki/Binoculars#Prism_binocularshttp://en.wikipedia.org/wiki/Multi-touchhttp://en.wikipedia.org/wiki/Gonioscopyhttp://en.wikipedia.org/wiki/Corneahttp://en.wikipedia.org/wiki/Iris_(anatomy)http://en.wikipedia.org/wiki/Gait_analysishttp://en.wikipedia.org/wiki/Fingerprinthttp://en.wikipedia.org/wiki/Light-emitting_diodehttp://en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope


5/5

tugas fisika (annisa x.6.06)

Documents