What is light
A person can see clearly in a mirror as it is transparent. But the person cannot see through its walls, floors, doors, or wooden windows because they are opaque. In a dark room, everything appears invisible to the eyes as when light falls in a direction it is reflected and comes to the human eyes. So light is a type of energy that allows the eyes to see properly. During the day, the main form of light is the Sun and the second form of light is the glow of the light. Other frequent sources are fire, electric bulbs, tubelights, compact fluorescent lamps and luminous electron tubes. The objects that have their own light are called luminous objects. Sun, stars, bulb, tubelight and candle flame. The objects that don't have their own light but throw back the light that falls on them are called non-luminous objects. Tables, chairs, animals, plants, planets, satellites, the moon, football, cricket ball, tennis ball, basketball, and bat are non-luminous objects. The object that only reflects and absorbs light but does not pass through it is known as an opaque object. If a person tries to view through an opaque object, they won't be able to see the other side of the opaque object. The object that enables a minor portion of light to pass through it is known as a translucent object. When the light rays hit a translucent object, some light passes through it and other light is thrown back and absorbed in various ways. Objects seen through translucent objects, do not look simple and fresh. They appear hazy which means a person cannot see through a translucent object in a simple way. The objects through which light passes are seen clearly. Only a minor portion of light is absorbed and thrown back by transparent objects and the majority of light passes through them.
Attributes of light
- Light is a type of energy that moves in the form of ripples.
- Light waves move in every direction as they draw back from the source.
- Light can move via an open space without requiring a solid, liquid or gaseous form.
- From any source of light rays move in a direct line known as rectilinear propagation of light.
- Light moves via a gap at the fastest speed, about 300000 km/s or 3*10^8 m/s. The speed of light is shown in an objective model by the letter ‘c’.
What are shadows
It does not matter whether the light is from the Sun or a lamp indoors, light moves in a straight line. If a candle is lit, and placed in the hand, the shadow of the hand will be visible on the wall. The light moves through the candle; the hand cannot move through the light. Though the light is visible on the wall, the area of the hand blocks the light so light is formed via shadow.
Properties of Shadow
- Shadow is always dark and does not vary with the colour of the object or the light.
- A shadow is always created in the way opposite direction to the light source.
- Shadow always highlights the profile of the object and does not provide any detail about the object.
- The dimensions of the shadow vary with the distance between the object and the screen.
Creation of Image
An image is created when light rays move from the object and merge or appear to meet at a point after being reflected from the mirror. The image is created on the screen when light rays merge at a point called the real image. The image when light rays don't merge at a point and are not created on the screen, is known as a virtual image. A pinhole camera is equipment used to get an image on the screen. It consists of a rectangular box created by a wooden object, cardboard or metal. It's one surface is substituted with a translucent material. This surface works as the screen on which the image is created. A tiny pinhole is created on the side opposite the ground glass which permits light from the object to enter the box. The smaller the camera, the smaller the image would be created. The larger the camera, the larger the image would be. Transforming the length of the pinhole camera, transforms the dimension of the image.
Reflection of light
As the light strikes the object, some of the light is reflected back from the object. The light moves back to the eye and allows it to see the object. Reflection is the scattering of light rays off a surface.
