Revision Notes of Ch 11 Light, Shadows and Reflections Class 6th Science
- Light
- Luminous objects
- Non-Luminous objects
- Transparent, Opaque and Translucent Objects
- Characteristics of light
- Shadow and its properties
- Pinhole camera
- Mirror and types of mirror
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
(i) Luminous object: The objects which emit their own light is called luminous object.
→ Example: sun, torch bulb, star
(ii) 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:
(i) Transparent
(ii) Translucent
(iii) Opaque
(i) Transparent
→ These objects allow light to pass through them in straight line completely.
→ We can see through these objects clearly.
→ Examples: air, water, etc.
(ii) 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.
(iii) 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
(i) Image formed by a pin hole camera is coloured.
(ii) Image formed by a pin hole camera is inverted.
(iii) 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
(i) Ray of light: It is a path along which light travels in the given direction.
(ii) 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
(i) Plane mirror: Image formed is of the same size
(ii) Concave mirror: Reflecting surface is bent–in.
(iii) 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.