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# laws of reflection and refraction

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## Ahmed El-sheemy

on 15 December 2014

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#### Transcript of laws of reflection and refraction

Laws of
reflection and refraction

The law of reflection
The refracted ray lies in the same plane as the incident ray and the surface normal
The law of refraction
The ray of light approaching the mirror is known as the
incident ray
.
The ray of light that leaves the mirror is known as the
reflected ray
.
At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror. This line is known as a
normal line
.
The normal line divides the angle between the incident ray and the reflected ray into two equal angles.
The angle between the incident ray and the normal is known as the
angle of incidence
.
The angle between the reflected ray and the normal is known as the
angle of reflection
.

The law of reflection states that when a ray of light reflects off a surface:

The reflected ray lies in the same plane as the incident ray and the surface normal
(ie, the reflected ray lies in the plane of incidence)

The angle of incidence , i, equals the angle of reflection , r.
The law of reflection (cont,)
The law of refraction"SNELL's law" states that:
The amount of bending depends on the indices of refraction of the two media and is described quantitatively by Snell's Law.
A light-ray always deviates more towards the normal in the optically denser medium: i.e., the medium with the higher refractive index.
The law of refraction
By
Dr \ Ahmed El-Sheemy
Ophthalmology resident
Damanhour Ophthalmology hospital

The law of refraction
The ray of light approaching the interface is known as the
incident ray
.
The ray of light that leaves the interface is known as the
refracted ray
.
At the point of incidence where the ray strikes the interface, a line can be drawn perpendicular to its surface. This line is known as a
normal line
.
The normal line divides the angle between the incident ray and the refracted ray into two equal angles.
The angle between the incident ray and the normal is known
as the
angle of incidence
.
The angle between the refracted ray and the normal is known
as the
angle of refraction
.

Total internal reflection
occurs when light travels from a high-index medium to a low-index medium and the angle of incidence exceeds a certain critical angle.
Under these circumstances, the incident ray does not pass through the interface; all light is reflected back into the high-index medium.
The law of reflection governs the direction of the reflected ray.
The critical angle is the angle of incidence that produces a transmitted ray 90° to the surface normal.
The critical angle is calculated from Snell's law:
is the bending of a wave when it enters a medium where its speed is different.
If a light wave passes from a medium in which it travels slow into a medium in which it travels fast, then the light wave would refract away from the normal.
On the other hand, if a light wave passes from a medium in which it travels fast into a medium in which it travels slow, then the light wave will refract towards the normal.
Bouncing back of a light ray after hitting an interface between 2 media
Full transcript