Reflection of Light:

Objectives:

1.    Compare regular and diffuse reflections.

2.    Explain how concave and convex mirrors from images.

3.    List several uses of concave and convex mirrors.

Resources:

Notes:

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.

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.

(spaceguard.ias.rm.cnr.it/.../dictionary/ img/reflection.gif)    /    (www.arts.richmond.edu/.../pedagogy/ 132/132notes/fig201.gif)

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

(www.ijvs.com/volume1/ edition5/reflec4.gif)

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

(www.williamson-labs.com/images/ refraction-fish.gif)

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

(micro.magnet.fsu.edu/primer/images/ refraction/refangle.jpg)