فيزياء التشابتر٦ فاينل

54問 • 2年前

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Light is

stream of particles that either was emited yb the object being viewed ro emanated from hte eyes of hte viewer.

The light energy si

na overflow of fine particles that emti orfm hte light source and travel ni straight lines ni hte homogeneous meduim whti great sped.

Light moves through hte transparent media and reflects in the

bright objects.

When Lgiht fals no hte eye, it causes a

sense of vision.

Newton particle model of light: Model advantage:

Explain reflection and refraction of light

Newton particle model of light: Model disadvantage:

Newtons' asumption that hte sped of lightni light-dense media si greater than ni light-slight media, whcih later proved ot be amistake ni practice.

Planck model

having hte some properties of particle model and wave model

Lgiht mutsebregarded sahavnig a

adual nautre.

Light exhibits the characteristics of a wave ni some situations and the characteristics of aparticle in other

situations.

the energy foagilht

wvaesipresenetdni particles caeld photns.

photoelectric efect:

when light strikes ametal surface, electrons are sometimes. ejected orfm hte surface.

hte kinetic energy of an ejected electron

depend no hte frequency of light and si independent of hte light intensity.

The incident ray, the reflected ray, and the normal (N) all are lying in the

same plane.

Refraction of Light:

When a ray of light traveling through a transparent medium encounters a boundary leading another into transparent medium, part of the energy is reflected and part enters the second medium.

The ray that enters the second medium changes its direction of propagation at the boundary and is said to be.

refracted

The refracted ray is bent toward the normal because the speed of the light in the first medium v1 is

faster than the speed of the light in the second medium v2.

The speed of light

in any material is less than the speed in vacuum

light travels at its maximum speed in

vacuum.

index of refraction is a

g number greater than unity because v is always less than c and n is equal to unity for vacuum.

Snell's law of refraction:

When light travels from one medium to another, the speed changes v=c/n, but the frequency is constant. So the light bends

occurs when light travels from a dense medium of high index of refraction to a light medium of lower index of refraction in which the angle of incident at the boundary between dense medium and light medium is greater than the critical angle ic

Total internal reflection

critical angle

ic is an particular angle of incidence lin the denser medium), in which angle of refraction lin the light medium) equals to 90°

An interesting application of total internal reflection is the use of glass or transparent plastic rods

"Optical Fibers" to transport light from one place to another

Optical fiber devices are particularly useful for viewing an object at an inaccessible location. For example:

Physicians often use such devices to examine internal organs of the body.

Lenses

are commonly used to form images by refraction in optical instruments

Lenses such as

cameras, telescopes, and microscopes.

Thin lens is

one whose thickness is small compared to the radi of curvature R.

The focal length f:

of a thin lens is the distance from the center of the lens to the focal point.

The power of lens,

P, is the reciprocal of its focal length: P= 1/f

Converging lenses have

positive focal length and are thicker at the center than at the edge.

Diverging lenses have

negative focal length and are thinner at the center than at the edge.

The lateral magnification (M) is the

ratio between the image height and the object height

.When M the object is positive

the image is upright and on the same side of the lens as the object

When M the object is negative,

the image is inverted and on the side of the lens opposite the object

Cornea and crystalline lens (eye lens system):

The two lens system.

Ciliary Muscle:

Controlling the curvature of the eye lens

Retina:

at the back of eyeball, like the film.

Pupil:

Variable aperture

Iris:

Controls the size of the pupil fully open at law light level and small opening at high light level

Optical nerve:

delivering the generated signal to the brain

Most of the refraction occurs at the outer surface of the eye, where the cornea is

covered with a film of tears.

Accommodation is the

process of adjusting the eye's focal length to produce the picture on the retina.

The near point is

the closest distance (- 25 cm) for which the lens can accommodate to focus light on the retina

The far point of the

eye represents the greatest distance for which the lens of the relaxed eye can foous light on the retina.

The near point of a farsighted eye is

much greater than 25 cm and thus see faraway objects clearly but not nearby objects.

This Farsightedness can be corrected by placing a

converging lens in front of the eye.

Nearsightedness (myopia):

The person can focus on nearby objects, but not on faraway objects

The maximum focal length of the nearsighted eye is

insufficient to produce a sharp image on the retina, and rays from a distant object converge to a focus in front of the retina.

This Nearsightedness can be corrected by placing a

diverging lens in front of the eye.

Old-age vision (presbyopia) is

the reduction in accommodation ability with age a visual muscles weaken and the lens hardens.

Old-age vision can be corrected with

converging lenses.

Astigmatism:

A common vision condition that causes blurred vision.

Astigmatism is an

irregularly shaped cornea or lens that prevents light from focusing properly on the retina

I-Lenses that have different curvatures in different planes 2-Glasses of Cylindrical lens + spherical lens

Astigmatism can be corrected with:

كويز الاسلامية١

Yoo Banana · 26問 · 2年前

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