P8: Light

How an optical image is formed in a plane mirror:The image appears to be the same distance behind the mirror as the real object is in front of the mirrorThis is the reason why: The brain thinks the light travels in straight lines without changing directionTherefore, this is a virtual image. This is because the light rays never really go there.

Characteristics of an optical image formed in a plane mirror:The image is the same size as the objectIt is the same distance from the mirror as the objectA line joining equivalent points of the image and object meet the mirror at a right angleIt is virtual

Laws of reflection:Angle of incidence = Angle of reflectionThe incident ray, reflected ray, and normal are always on the same plane 

An experimental demonstration of the refraction of light:

What is the critical angle:The angle at which the refracted ray is parallel to the surface of the material

Total Internal Reflection:When the light ray tries to move from glass to air at an angle greater than the critical angle, the refracted ray cannot escape from the glass.Therefore, refraction cannot happen. All the light is reflected at the glass.

Internal Reflection:Occurs inside the material

Optic Fibers:How does it work:When light enters at one end of the fiber, it strikes the surface of the glass at an angle greater than the critical angle. Total internal reflection occurs at the glass surface and they cannot escape until it reaches the other end. Uses:Telecommunications: Pulses (little bits of light) are sent along the optic fiber in the form of digital signals, which contain digital information. Optic fibers have a greater capacity than copper wires.Medicine: They are used in endoscopes. They take light down at the end of the endoscope to light inside the body. Other optical fibres in the bundle collect the reflected light using lenses.The reflected light is sent along the fibres to a computer which displays the information as a picture on a monitor.

Focal length: the distance from the focal point to the center of the lendsPrincipal Focus

How is light

How is l

How is light dispersed in a glass prism?The sides of a prism are not parallel. So, when light is refracted by a prism, it comes out in a different direction. It is deviated. If a narrow beam of white light is passed through a prism, it splits into a range of colors called a spectrum. 

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