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"Light Reflection and refraction"
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You can have a view of yourself if you look into
a mirror.
calm water surface.
a piece of shiny metal wall.
a piece of window glass.
Now you look into a mirror and see the image of yourself.
In front of the mirror.
On the surface of the mirror.
Behind the mirror.
A ray of light bounces off a plane mirror.
mirror
This is an example of reflection of light.
reflected rayincident ray
normal
mirror
angle of incidence
angle of reflection
• The incident ray, the reflected ray and the normal all lie in the same plane.
normal
incident ray reflected ray
mirror
normal
incident ray reflected ray
mirror
normal
incident ray reflected ray
mirror
• angle of incidence angle of reflection =
Regular reflection
parallel incident rays
parallel reflected rays
• on a flat, smooth surface• e.g. mirror
Regular and diffuse reflection
Diffuse reflection
• on a rough, not perfectly smooth surface
• e.g. cover of a book
parallel incident rays
reflected rays in different directions
Regular and diffuse reflection
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The
phenomenon is mainly in governance to the law of conservation of energy. The proper explanation
would be that due to change of medium, the phase velocity of the wave is changed but
its frequency remains constant. This is most commonly observed when a wave passes from one medium to another at any angle other than
90° or 0°. Refraction of light is the most commonly observed phenomenon, but any type of wave can
refract when it interacts with a medium, for example when sound waves pass from one
medium into another or when water waves move into water of a different depth.
The incident ray, the refracted ray and the normal to the surface at the point of incidence all lie in one plane.
For any two given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant.
And the third law is called Snell’s law
Snell's law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water and glass.
Snell's law states that the ratio of the sins of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media, or equivalent to the opposite ratio of the indices of refraction:
with each θ as the angle measured from the normal, v as the velocity of light in the respective medium (SI units are meters per second, or m/s) and n as the refractive index (which is unit less) of the respective medium.
