Reflection of Light:


    1.    Compare regular and diffuse reflections.

    2.    Explain how concave and convex mirrors from images.

    3.    List several uses of concave and convex mirrors.




Reflection of light:  

When light reaches a solid object one of the things that can happen is that the light can be reflected.  The reflected light can be either partially or completely reflected based on the elasticity of the material.  For this reason, metals make good reflective surfaces.  

Cartoon: Looking in a mirror

Law of reflection:

The law of reflection states that the angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal.


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This law applies to regular, partial and diffuse reflection.

Regular Reflection:

Regular reflection describes reflection off of very smooth surfaces.  It is the type of reflection that can be seen with a mirror or off of a lake on a day without any wind.  Here are a few conditions that are true regarding regular reflection.

Regular reflection is reflection off of a very smooth opaque surface

Angle () of incidence = of reflection

The image looks exactly like the object


Diffuse Reflection:  

When light is incident off of a rough or irregular surface, it can be defined as irregular of diffuse reflection.  This occurs hen you look at the same lake on a windy day.

Diffuse reflection is reflection off of a rough or irregular opaque surface

Reflected rays are scattered

The formed image is not clearly defined

The of incidence = of reflection.  The difference is that the surface is filled with different angles.


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Refraction of Light:

Refraction is defined as the bending of light due to a change in its speed.  This is why a straw appears bent in a glass of water or why a swimming pool appears shallower than it really is.  The differences in the position and dimensions are considered apparent because they have not actually changed.  The differences are caused by the changing speed of the light as it transitions to different media.

Remember that light (like all waves) travels at constant speed within a medium

The speed changes as light changes medium

Light travels faster in less dense mediums

In less dense mediums the light moves away from the normal

Moves slower in more dense mediums

In more dense mediums the light moves towards the normal


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Index of Refraction:

The index of refraction is a measure of the relative speed change from air to a different mediumThe greater the change in speed the greater the index of refraction.

Air is given the relative index of 1

The higher the speed change the higher the index value

Material Refractive Index
Air 1.0003
Water 1.33
Glycerin 1.47
Immersion Oil 1.515
Glass 1.52
Flint 1.66
Zircon 1.92
Diamond 2.42
Lead Sulfide 3.91



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