االنكسار

Keywords المصطلحات

انكسار1.

شعاع ساقط2.

شعاع منكسر3.

عمود االنكسار4.

زاوية السقوط5.

زاوية االنكسار6.

معامل االنكسار7.

قانون سنل8.

القانون الثاني لالنكسار9.

Goals األهداف

فهم طبيعة االنكسار1.

يفسر الظواهر المتعلقة باالنكسار2.

معامل االنكسار و حساباته3.

رسم مخططات الصورة المتكونة في 4.العدسة الرقيقة.

تعيين موضع الصورة و صفاتها5.

حساب الزاوية الحرجة6.

االنعكاس الكلي الداخلي7.

الظواهر الجوية المتعلقة باالنكسار8.

Refraction االنكسار

Assessment

Assessment

5. In each diagram, draw the "missing" ray (either incident or refracted) in order to appropriately show that the direction of bending is towards or away from the normal.

انكسار القلم

http://www.flickr.com/photos/physicsclassroom/5079912762/

Assessment6.Arthur must aim at a position on the water below where the fish appears to be. Since light refracts away from the normal (water to air) as Arthur sights at the fish, the refracted ray when extended backwards passes over the head of where the fish actually is.

=angle of incidence    

=angle of refraction    

Thin lenses

في :- سميكة ال̀مــة عدسةالحافة عند رقيقة الوسط،

في :- رقيقة مcفرbقة عدسةالحافة عند سميكة الوسط،

f f

f f

1

f f2f 2f

f < o< 2f i > o

f f2f2f

O > 2f 2f > i > f

2

f f2f2f

o= 2f i = o 3

f f2f2f

i = f o = 4

f f2f2f

o< f i > o 5

f f2f

O >> 2f i f6

f

7

f f

8

صغيرة – – الضوء سرعة بارد هـــواءعن – يبتعد الشعاع كبيرة الضوئية الكثافة

العمود

كبيرة – – الضوء سرعة ساخن هـــواءعن - يبتعد الشعاع صغيرة الضوئية الكثافة

العمود

Observer

Apparent position of sun

Earth

Actual position of sun

Atmosphere

Lingering daylight after the sun is below the horizon is another effect of refraction. Light travels at a slightly slower speed in Earth’s atmosphere than in space. As a result, sunlight is refracted by the atmosphere. In the morning, this refraction causes sunlight to reach us before the sun is actually above the horizon. In the evening, the

Sunlight after Sunset

Different “shapes” of Sun

sunlight is bent above the horizon after the sun has actually set. So daylight is extended in the morning and evening because of the refraction of light. Note: the picture greatly exaggerates this effect as well as the thickness of the atmosphere.

28

• Plastic or glass rods are used to “pipe” light from one place to another

• Applications include:– medical use of fiber

optic cables for diagnosis and correction of medical problems

– Telecommunications

Total Internal Reflection: Application

Fiber OpticsTotal Internal Reflection( )incidence cr

30

• The incident ray, the refracted ray, and the normal all lie on the same plane

• The angle of refraction is related to the angle of incidence as

– v1 is the speed of the light in the first medium and v2 is its speed in the second

Refraction – Snell’s Law

2 2

1 1

sin

sin

v

v

Since and , we get

, or

11

cv

n 2

2

cv

n

index of refraction

2 2 2 1

1 1 1 2

sin /

sin /

v c n n

v c n n

2 2 1 1sin sinn n

Snell’s Law

العمودالساقط الشعاع المنعكس الشعاع

المنكسر الشعاع

UCSD: Physics 8; 2006 31Spring 2006

n2 = 1.5

n1 = 1.0

A

B

Refraction at a plane surface• Light bends at interface between refractive

indices– bends more the larger the difference in refractive

index– can be effectively viewed as a “least time” behavior

• get from A to B faster if you spend less time in the slow medium

1

2

Experts only:n1sin1 = n2sin2

انكسار :- زاوية تقابلها التي السقوط زاوية الحرجة الزاوية (90oقائمة)

كبيرة :- الضوئية كثافته وسط من الشعاع سقوط شرطهاضوئية كثافة أقل آخر وسط نحو

UCSD: Physics 8; 2006 33Spring 2006

Total Internal Reflection• At critical angle, refraction no longer occurs

– thereafter, you get total internal reflection– for glass, the critical internal angle is 42°– for water, it’s 49°– a ray within the higher index medium cannot escape at

shallower angles (look at sky from underwater…)

n2 = 1.5

n1 = 1.0

42°

incoming ray hugs surface

2 1

المرض

الصفة

العالج