Why angle of incidence equal to angle of reflection

In summary, the law of reflection states that the angle between the incident ray and the reflecting surface normal is equal to the angle between the reflected ray and the reflecting surface normal. This law is based on the Fermat principle, which states that the path taken between two points by a ray of light is the path that can be traversed in the least time.
  • #1
prashant13b
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I want to why in ray optics. Angle between incident ray and reflecting surface normal is equal to angle between reflected ray and reflecting surface normal. Simply why angle of incidence is equal to angle of reflection?
 
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prashant13b said:
I want to why in ray optics. Angle between incident ray and reflecting surface normal is equal to angle between reflected ray and reflecting surface normal. Simply why angle of incidence is equal to angle of reflection?

ReflRefr.gif


http://www.physics.ucdavis.edu/Classes/Physics9B_Animations/ReflRefr.html

 
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  • #3
A.T. said:
http://www.physics.ucdavis.edu/Classes/Physics9B_Animations/ReflRefr.html


This law was made before the evolution of wave optics. I want answer on basis of classical physics
 
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  • #4
Write Maxwell equations and apply them to the inner and outer medium. One out of three consequences you get would be the equality of incident and reflected angles. Let me know if it is not clear.
 
  • #5
prashant13b said:
I want to why in ray optics. Angle between incident ray and reflecting surface normal is equal to angle between reflected ray and reflecting surface normal. Simply why angle of incidence is equal to angle of reflection?
Ray Optics is based on Fermat Principle. http://en.wikipedia.org/wiki/Fermat's_principle
In the simplest form it states that the light ray travels along a path between two points which needs the shortest time.
In optics, Fermat's principle or the principle of least time is the principle that the path taken between two points by a ray of light is the path that can be traversed in the least time. This principle is sometimes taken as the definition of a ray of light.[1] However, this version of the principle is not general; a more modern statement of the principle is that rays of light traverse the path of stationary optical length with respect to variations of the path.[2] In other words, a ray of light prefers the path such that there are other paths, arbitrarily nearby on either side, along which the ray would take almost exactly the same time to traverse.[3]

See picture. You want the light reach from A to B in the way that it is reflected from the horizontal mirror. How can you draw the the light ray so it reaches B in the shortest time? It must travel along the shortest path.
Draw the mirror image of B: it is B'. Connect A and B' with a straight line. The line segment AB' is the shortest of all possible paths between A and B'.
AB' intersects the mirror at C. Connect C with B. The length of CB is equal to CB'. So the length of the path ACB is the shortest possible between A and B which touches the mirror. The three alpha angles are congruent, so the beta-s are also equal (##\beta=90-\alpha##
Fermatrefl.JPG
)ehild
 

FAQ: Why angle of incidence equal to angle of reflection

1. Why is the angle of incidence equal to the angle of reflection?

The angle of incidence and the angle of reflection are equal because of the law of reflection, which states that the incident angle and the reflected angle are always equal in a reflection. This law is a fundamental principle in optics and is based on the conservation of energy and momentum.

2. What is the significance of the angle of incidence being equal to the angle of reflection?

The equal angles of incidence and reflection have significant implications in the field of optics. This phenomenon allows for the prediction and manipulation of light behavior, such as in the design of mirrors, lenses, and other optical devices.

3. Can there be any exceptions to the law of reflection?

The law of reflection holds true for most surfaces, but there are some exceptions. For example, when light reflects off a rough surface, the angle of reflection can vary due to the irregularities in the surface. Additionally, at the atomic level, the law of reflection may not apply due to the wave-like behavior of light.

4. How is the angle of incidence and reflection measured?

The angle of incidence and reflection are measured from the normal, which is a line perpendicular to the surface at the point of incidence. These angles are typically measured in degrees using a protractor or other measuring device.

5. Why is the angle of incidence and reflection important in everyday life?

The concept of the angle of incidence and reflection is important in many everyday applications, such as in mirrors, lenses, and other reflective surfaces. It allows us to see objects and images, and also plays a crucial role in the functioning of many optical devices, such as cameras and telescopes.

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