NCERT Summary: Light, Shadow & Reflection | Science Class 6 PDF Download

Light

• It is a form of energy which is responsible for seeing objects.
• When light falls on an object, some light get reflected, this reflected light come to our eyes and we are able to see an object.
• Example: sun, torch, candle, fireflies and glow worm etc.

Sources of light

• Luminous object: The objects which emit their own light is called luminous object.
  Example: sun, torch bulb, star
• Non-luminous object: The objects which do not emit their own light is called non-luminous object.
  Example: Moon, shoe, trees.

Types of materials transmit light

There are three types of materials which transmit light:

• Transparent
• Translucent
• Opaque

1. Transparent

• These objects allow light to pass through them in straight line completely.
• We can see through these objects clearly.
• Examples: air, water, etc.

2. Translucent

• These objects allow light to pass through them partially.
• The object is not clearly seen in translucent object.
• Examples: Tissue paper, frosted glass, butter paper, etc.

3. Opaque

• These objects do not allow light to pass through them.
• We can’t see the object through this.
• Examples: wall, door, trees etc.

Characteristics of light

• Light travels in straight line
• Light can be reflected
• Light can be bent
• The speed of light is 3 × 108 m/sec
• Light can be polarized

Shadow

• When an opaque object blocked the path of light it forms a dark portion on the opposite side of the object this dark portion is known as shadow.

Properties of shadow

• The object must be opaque or translucent
• Transparent object do not make shadow
• It is dark in color
• It is formed opposite to the source of light
• It gives the information about the shape of object
• Size of shadow can be increase or decrees by change in distance between object and screen are changed.

Pin hole camera

• It is a toy device use to study light travels in straight line

Properties of image formed by a Pin Hole Camera

• Image formed by a pin hole camera is coloured.
• Image formed by a pin hole camera is inverted.
• Image formed by a pin hole camera is smaller in size.

Rectilinear propagation of light

• Light travels in a straight line are called rectilinear propagation of light.

Important terms regard rectilinear propagation of light

• Ray of light: It is a path along which light travels in the given direction.
• Beam of light: Bunch of ray of light travel in the given direction.

Mirror

• A mirror is a polished surface which can make the image of an object.

Types of Mirror

• Plane mirror: Image formed is of the same size
• Concave mirror: Reflecting surface is bent–in.
• Convex Mirror: Reflecting surface is bulged-out.

Reflection

• When light falls on a mirror, light wave may change their direction upon the striking surface this phenomena is called reflection.