Chapter 11 Light, Shadows and Reflections Class 6 Notes science

Topics in the chapter

• 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.

• Objects that do not produce their own light but are visible when reflect light falling on them are called Non-Luminous Objects. Example – Table, planets. Non-luminous objects can be classified as-

Shadows are dark regions formed when an opaque object blocks the path of light. This formation is possible only because light only travels in a straight line.

How to make a Pinhole Camera?

Step 1: Take two cardboard boxes one larger than the other such that one box slides into the other without any gap.

Step 2: Cut out open one side of each box. On the opposite side of the larger box cut a small hole in the centre.

Step 3: On the opposite side of the smaller box cut a square of about 5 cm and cover this open area with a tracing paper.

Step 4: Slide the smaller box inside the larger one such that the side with the tracing paper is on the inside.

Step 5: Cover the camera and your head with a black cloth and then get ready to observe the distant objects.

Fig: A Pinhole Cameria

It is a simple camera with a small aperture and forms an inverted image of the object.

Mirrors and Reflections

All of us are used to seeing a mirror every day. The image that we see in a mirror is called Reflection. The mirror deflects the direction of the light that falls upon it.

Fig: A Mirror Changing the direction of light as it falls on it