Category : 6th Class
Light, Shadow and Reflection
Light is a form of energy visible to the human eye that is radiated by moving charged particles. Speed of light in air is about 3 x m/s.
Ray: It is a very narrow and straight path of light.
Beam: It is broader and consists of several rays.
Sources of Light
The objects which give out light are called sources of light. Sun, star, bulb, torch, candle lantern, lamp, etc. are the sources of light.
Luminous and Non-luminous Objects
The objects which produce their own light are called luminous objects. Sun, stars, bulb, torch, candle, lantern, lamp etc. are luminous objects.
The objects which do not produce light on their own are called non-luminous objects. Table, fan, book, chair, etc. are non-luminous objects.
Transparent, Translucent and Opaque Objects
Transparent Objects: The objects which allow light to pass through them. For example glass, water, air, etc.
Translucent Objects: The objects which allow light to pass through them partially. For example, oiled paper, tissue paper, muddy water, ground glass, etc.
Opaque Objects: The objects which do not allow light to pass through them. For example, wall, blackboard, metal sheet, etc.
If an object is placed in front of a source of light, the object cast its shade which known as shadow. All the opaque objects produce their shadow on the opposite side to the source of light. The shape of shadow depends on the followings:
Reflection of Light
When a ray of light falls on the surface of a mirror, they are sent back. This phenomenon is known as reflection of light.
The ray which falls on the surface of a mirror is called an incident ray. The ray which is sent back after reflection is called reflected ray.
A spherical mirror is a mirror which has the shape of a piece cut out of a spherical surface. There are two types of spherical mirrors: concave and convex.
Reflecting surface of a concave mirror bulges inward whereas reflecting surface of a convex mirror bulges outward.
The images which are inverted and can be taken on the screen are called real images
The images which are erect and cannot be taken on the screen are called virtual images.
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