Thursday, December 24, 2009

Reflection of light

Reflection occurs when a light ray bounces off a surface.

Terminology :

Incident ray is the incoming light ray.

Reflected ray is the light ray moving away from the surface .

The most important characteristic of these rays is their angles in relation to the reflecting surface. These angles are measured with respect to the normal of the surface.

The normal is an imaginary line perpendicular to the surface.

The angle of incidence, θi is measured between the incident ray and the normal.

The angle of reflection, θr is measured between the reflected ray and the normal.

When a ray of light is reflected, the reflected ray lies in the same plane as the incident ray and the normal.

Law of Reflection
The Law of Reflection states that the angles of incidence and reflection are always equal and
that the reflected ray always lies in the plane of incidence.

When you smile into a mirror, you see your own face smiling back at you. Did you notice that;
i. the size of the image is the same as you (object)
ii. the distance of the image seem as the same distance of you from the mirror.
iii. when you move your left hand, the image will move it right hand
iv. then you image never upside down .

worked example:
Question: An incident ray strikes a smooth reflective surface at an angle of 33◦ to the surface normal. Calculate the angle of reflection.

Step 1 : Determine what is given and what is required We are given the angle between the incident ray and the surface normal. This is the angle of incidence. We are required to calculate the angle of reflection.

Step 2 : Determine how to approach the problem
We can use the Law of Reflection, which states that the angle of incidence is equal to the angle of reflection.

Step 3 : Calculate the angle of reflection We are given the angle of incidence to be 33◦. Therefore, the angle of reflection is also 33◦.

quiz :


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