Light and the formation of shadows | Class 6 | Science | Chapter 13 | Maharashtra State Board
In this fascinating video, we will delve into the properties of light and explore the intriguing concept of shadows. We will start by understanding the difference between luminous and non-luminous objects, as well as artificial sources of light. Moving on, we will explore how light travels and the laws of reflection. With the help of a plane mirror, we will investigate how images are formed and reflected. Along the way, we will share some fascinating facts about the largest sundial and the Raman Effect. We will also travel back in time to learn about Newton's disc and the magic behind it. Whether you are a science enthusiast or simply curious about the world around you, this video is sure to captivate and engage you.
Questions & Answers
1. Choose an appropriate word and fill in the blanks.
(options : seven, star, through, transparent, opaque, colours, shape, erect, inverted, luminous, candle)
A star is a natural source of light.
A candle is an artificial source of light.
When a light passes through a prism, it gets separated into seven colours.
The image obtained in the pinhole camera is inverted.
A shadow is formed when an opaque object comes in the way of light.
When a transparent object comes in the way of light, light passes through it.
2. Write whether of following objects are luminous or non-luminous.
Object | Luminous / Non-luminous |
A book | Non-luminous |
A burning candle | Luminous |
A wax cloth | Non-luminous |
A pencil | Non-luminous |
A pen | Non-luminous |
A light bulb | Luminous |
A tyre | Non-luminous |
A torch | Luminous |
3. Match the following.
Group A | Answer | Group B |
Mirror | Reflection | Non-luminous |
Firefly | Luminous | Inverted image |
Pinhole camera | Inverted image | Reflection |
Moon | Non-luminous | Luminous |
4. Write the answers to the following.
(a) What things are necessary for the formation of a shadow?
Ans. The following things are necessary for the formation of a shadow. The source of light, an opaque object and a surface on which the shadow falls.
(b) When can an object be seen?
Ans. The light rays from the source of the light, fall on an object. When this light reflects from the surface of the object, it enters our eyes. Therefore, we are able to see this object. The luminous object can be seen as they emit their own light.
(c) What is shadow?
Ans. Shadow is produced by an opaque object. Light does not pass through an opaque object. It does not reach the wall or any other surface on the other side of the object. This part therefore remains dark. This dark area is called the shadow of that object.
E X T R A
1. Fill in the blanks.
The Sun is the main natural source of light.
White sunlight contains seven colors.
Light must be reflected from the surface of an object for the object to be seen.
Light travels in a straight line. This is called the linear propagation of light.
An object that emits light is called a luminous of light.
2. Find the odd one out.
(a) Fireflies, Crows, Honey mushroom, Angler fish.
Ans. Crows. (Crows are non luminous, others are luminous.)
(b) Moon, Mars, Sun, Earth.
Ans. Sun. (Sun is natural source of light, others are not.)
(c) Granite cladding of wall, Mirror, Clean and still water, Cardboard.
Ans. Cardboard. (Cardboard is non reflective, others are reflective.
(d) Flame of the candle, Fireflies, Lantern, Electric bulb.
Ans. Fireflies. (Fireflies are natural source of light, others are artificial source of light.)
3. State whether the following statements are true or false.
(a) The left right sides of the original object appear to be interchanged in the plane mirror image.
Ans. True.
(b) Stars are luminous.
Ans. True.
(c) The shadows are long in the afternoon.
Ans. False.
(d) Image in a pinhole camera is inverted.
Ans. True.
(e) We can see our image clearly in running water.
Ans. False.
4. Answer the following.
(a) How are shadows formed?
Ans. The shadow of an object is formed when the path of light is obstructed by an opaque object.
(b) Mention the factor on which the formation of a shadow depends.
Ans. The factors on which the formation of a shadow depends are:
Source of light.
Relative distance between the source of light, object and the screen or the surface on which the shadow is formed.
(c) Mention the characteristics of an image formed in a plane mirror.
Ans. The image formed in plane mirror has following characteristics:
The left and right sides of the object appears to be interchanged in the mirror image.
The distance between the object and the mirror is same as the distance between the image and the mirror.
The size of the image is the same as the size of the object.
(d) A shadow cast by an aeroplane or a bird cannot be seen when they are high above the earth. Why?
Ans.
A bird or an aeroplane is a small in size as compared to the natural sources of light. i.e. the sun
The distance between the earth (screen) and the bird or aeroplane (object) is very large.
The shadow does not reach the earth at all.
Hence, the shadow cast by an aeroplane or a bird cannot be seen on the ground as they are high above the earth.
(e) We get an inverted image of flame of a candle on the screen of a pinhole camera. Explain with the help of a diagram.
Ans.
Ans.
Light rays travel in a straight line.
The light rays passing across the lower part of the candle flame passes through the pinhole (C) and forms the upper part of the reflected image (B➝D).
Similarly, light rays passing across the upper part of the candle flame passes through the pinhole (C) and forms the lower part of the reflected image (A➝ E).
Therefore, we can see upside down (inverted) image (DE) of object (AB) formed on the screen of a pinhole camera.
4. Define the following.
(a) Reflection of light.
Ans.
The rays of light falling on an opaque object or translucent object are thrown back from the surface of the object. This is called reflection of light.
Shiny and smooth surfaces reflect more light while dull and rough surfaces reflect very little light.
We see the object when the rays reflected from the object reach our eyes.
(b) Luminous object.
Ans. The objects that emit light of their own or those which themselves are a source of light are called luminous objects. e.g.The sun and stars.
(c) Raman Effect / National Science Day.
Ans. Indian scientist Sir C.V. Raman presented research work regarding scattering of light is known as the ‘Raman Effect’. He discovered this effect on 28th February 1928. To commemorate this event, 28th February is celebrated as ‘National Science Day’ in India.
5. Differentiate between transparent, translucent and opaque object.
Transparent object | Translucent object | Opaque object |
All incident light rays falling on them pass throug them. | Some of the incident light rays falling on them pass through them and some get reflected. | Incident light rays falling on them do not pass through them and hence get reflected. |
e.g. Air, Pure water, transparent glass, etc. | e.g. Frosted glass, butter paper, tracing paper, etc. | e.g. A piece of cardboard, wooden desk, etc. |
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