TS 6th Class Science 15th Lesson Questions and Answers Telangana – Light, Shadows and Images

Light, Shadows and Images – TS 6th Class Science 15th Lesson Questions and Answers Telangana

Question 1.
Classify the following objects into transparent, translucent and opaque :
Cardboard, duster, polythene cover, oily paper, glass, spectacle lens, piece of chalk, ball, table, book, window glass, palm, school bag, mirror, air, water. (Conceptual understanding)
Which type of materials do you find more in your surroundings ? 2 M
Answer:

I find opaque materials more in my surroundings.

Question 2.
Hold a glass slab at one end with your hand and stand in sunlight. See the shadows of your hand and glass slab. Explain what you observed. (Experimentation) 2 M
Answer:

1. We can see the shadow of our hand on the ground.
2. We can not see the shadow of glass slab.
3. Glass slab is transparent and so sunlight passes through it without forming its shadow.

Question 3.
We cannot identify the presence of completely transparent objects even in the light. Is it correct or not? Support your answer. (Conceptual Understanding) 2 M
Answer:
Yes, we cannot identify the presence of completely transparent objects even in the light.
Eg:

1. Air cannot be seen.
2. Light transmitted through certain matter like air doesn’t reach our vision.
3. I can support the given statement.

Question 4.
Why can’t we see objects which are behind us? (Conceptual Understanding) 2 M
Answer:

1. Our body is opaque. Light cannot pass through it.
2. So the light reflected by those objects does not reach our eyes.
3. So we can’t see the objects lying behind us.

Question 5.
If we focus a coloured light on an opaque object, does the shadow of the object posses colour or not? Predict and do the experiment to verify your predictions (coloured light can be obtained by covering torch glass with transparent coloured paper) (Asking questions and making hypothesis) 2 M
Answer:

1. The shadow is not coloured. It is dark only.
2. Because, a ‘shadow’ means, ‘absence of light of any colour’.
3. Shadow is colourless irrespective of colour of the object.
4. It is predicted and proved correct after verifying the experiment.

Question 6.
Between an electric bulb and a tube light, which forms sharp shadows of objects? Do experiment to find and give the reason. (Conceptual Understanding) 4 M
Answer:

1. Electric bulb forms sharp shadows of objects.
2. A tube light cannot form sharp shadows of objects.
3. The same thing is proved correctly after doing the experiments.
4. Bulb light is a point source of light and it forms sharp shadow of the object.
5. Tube light is an extended source of light and so it cannot form sharp shadows of objects.
   (Note : Bulb = filament bulb)

Question 7.
What is required to get a shadow of an opaque body? (Conceptual understanding) 2 M
Answer:
Three things are required to get a shadow of an opaque body,

• Source of light
• Opaque object
• Screen

Question 8.
How can you explain the straight line motion of the light?
(Conceptual Understanding) /Experimentation and field investigation)2 M
Answer:

1. Light travels in a straight line. That is why, when opaque objects obstruct the light, their shadows form.
2. We can predict the shapes of the shadows only when we consider that light travels as rays along a straight path.
3. Formation of an ‘inverted image’ on the screen of the pinhole camera explains that light travels in a straight line.

Question 9.
Explain, what happens if the size of the hole in a pinhole camera is as big as the size of a green gram. Increase the size of the hole in pinhole camera and look at any object with that camera. What do you find? Write reasons for that. (Asking questions and making hypothesis) 2 M
Answer:

1. If the size of the pinhole camera is as big as the size of a green gram, the sharpness in the image decreases.
2. The image becomes thick and the details of the image are not visible.
3. As the size of the hole increases more light enters and disturbs the formation of the image.

Draw the shadows in your note book for the objects given below assuming that the light source is exactly above on these objects.

Question 10.
Draw the shadows in your note book for the objects given below assuming that the light source is exactly above on these objects. (Communication through drawing and Model Making) 8 M

Answer:

Question 11.
Where do you find reflection of light in your daily life? Write few examples. (Conceptual Understanding) 2 M
Answer:

1. The image of our face in the plane mirror is due to reflection of light.
2. The visibility of object in and around us.
3. The moon is visible to us because it reflects the sunlight.

Question 12.
We would not be able to see any object around us if light does not get reflected. How do you appreciate this property of objects? (Appreciation and aesthetic sense and values) 2 M
Answer:

1. Objects are visible only when light falls on it gets reflected and reaches our eye.
2. In darkness the objects are not visible as no light reaches our eyes from the objects.

Question 13.
Can we use a plain mirror as a rear view mirror? If not, why? (Asking questions and making hypothesis) 2 M
Answer:

1. We can’t use a plain mirror as a rear view mirror.
2. It can’t give a full rear view. So a convex mirror is used.
3. The convex mirror gives a small erect image.
4. Convex mirror has a capacity of minimising the rear object and catch in it.

Question 14.
A mirror is kept on the wall of your room. Your friend is sitting on a chair in that room. You are not visible to him in the mirror. How do you adjust your place so that you are visible to your friend in the mirror? Explain. (Experimentation and field investigation) 4 M
Answer:

1. Suppose my friend is sitting to the left side of the mirror fixed on the wall, at a distance.
2. Then I move to the right side of the mirror, till I am visible to my friend.
3. I sit in a position to fall incident ray from me on to the mirror.
   

Question 15.
Why do we get shadows of different shapes for same object? (C.U) 2M
Answer:

1. We can get shadows of different shapes for the same object, by changing its position.
2. Reason: It is because, light travels in a straight line path, in that path only shadows form.

Question 16.
What are the differences between a shadow and an image? (C. U) 4 M
Answer:

Question 17.
Malati noticed changes in lengths of her shadows during the daytime. She got some doubts about this. What could be those doubts? (Asking questions and making hypothesis) 4 M
Answer:
Possible doubts Malati may get.

1. From morning to noon (12 o’clock), the length of my shadow decreased gradually. Why so?
2. The position of my shadow also changed. Why so?
3. At noon, my shadow is just below me. Why so?
4. Again after the noon, the length of my shadow went on increasing with time. Why so?
5. The position of my shadow also changed, Why so?
6. Though I did not change my position, my shadow changed positions. Why so?

Question 18.
Observe the light source and mark the place where the screens should be kept to get the shadows of the objects given below. (Communication through drawing and model making) 8 M

Answer:

i) Screens should be placed at a distance from the objects.
ii) They should be placed just opposite to the light source.

TS 6th Class Science 15th Lesson Notes – Light, Shadows and Images

• We cannot see the objects in the absence of light.
• We can see an object only when light falls on it, bounces back and reaches our eye.
• Any object which burns or glows acts as a source of light.
• We need light to get the shadow of any object.
• We need a source of light, an opaque object and a screen, to form shadows.
• In many cases, we cannot guess the object by observing its shadow.
• Colour of objects cannot be determined by looking at their shadows.
• Shadow is always dark, whatever be the colour of the object.
• Light travels in a straight line. So shadows are formed.
• By changing its position, we can get shadows with different shapes for a single object.
• In a pinhole camera, we get an inverted image of the object.
• An image is different from a shadow.
• Light : It is a form of energy, which is released from sources of light such as sun, moon, bulb, candle etc.
• Sources of light : A substance which gives light is known as a source of light. Eg : sun, moon, bulb, etc.
• Shadow : A dark shape produced by an object on the effect of light rays. Shadows are formed when opaque objects obstruct the path of light.
• Transparent substances : The substance which we can see through is called transparent substance. They can not form shadows. Eg : air, glass etc. :
• Opaque substances : The substances through which we can not see it are called opaque substances. These can form shadows. Eg: card hoard, wall, etc.
• Pin hole camera : A camera through which we can observe a big object through a pinhole (very small hole). We get an inverted image in pin hole camera.
• Image : An image is a picture of someone or some thing.
• Reflection : When light falls on any object, it bounces back. This process is called reflection.