Properties of Light

Light is a form of energy that travels at the speed 300,000,000 m/s. Approximately 7.5 rounds of the earth in 1 second. Light travels in a straight lines within the same medium (or medium with the same optical density). Light is reflected when it hits an opaque surface. Light is reflected when it travels from one transparent medium to another.

REFLECTION OF LIGHT

Light which falls on an opaque object may be absorb or reflected. Reflection takes place when light rays which fall on the surface of an opaque object bounces off it. The amount and direction of the reflected light depend on the type of surface the light fall on.

Incident ray is the ray of light that approaches the surface. Reflected ray is the ray of light that bounces off the surface of an object.

Rough and uneven surfaces such as cloth and wood (right) cause diffused reflection (light reflection is scattered.

Smooth and flat surfaces such as mirrors, glass and shinny metals (left) cause regular reflection (light reflected regularly).

Application of reflection of light in daily life

Plane mirrors are used in bathrooms or bedrooms. Side mirrors and rear-view mirrors are used in cars. Convex mirrors give wider scope of view and used as security mirrors in shop and fish-eye mirrors at road bends. Concave mirrors magnify images and are  used in microscopes and telescopes. Periscopes are used to see above the water surface in submarines. A periscope consists of two plane mirror and change the direction of light. Kaleidoscopes form colourful images. They are made from two or more plane mirrors which reflect the light from objects placed between the mirrors.

1.      Convex mirror used in a supermarket

2.      Kaleidoscopes for kids

3.      View of pattern inside kaleidoscopes

REFRACTION OF LIGHT

Light can travel through transparent media such as air, water and glass. Light travels at different speeds in different media. When light travels from one medium into another, the change in the speed of light causes the light to bend or change direction. Therefraction of light is the bending of light as light travels through two types of media that have different densities (optical density).The speed of light increases when light enters a less dense medium meanwhile the speed of light decreases when light enters a denser medium. Refraction of light does not occur when the light ray is directly perpendicular to the surface of the medium (the light travel into the medium in the direction of the normal line), the light will pass through the medium in a straight line.

The refraction of light ray 

 Phenomenon of refraction of light. The pencil which is in water appear bended to the observer.

   

  Phenomenon of refraction of light. Scuba diver appear closer to the observer when it is in the water.