These AP 6th Class Science Important Questions 8th Lesson Light, Shadows and Reflections will help students prepare well for the exams.
Light, Shadows and Reflections AP 6th Class Science 8th Lesson Important Questions and Answers
Very Short Answer Questions (2 Marks)
Question 1.
How does a light ray travel?
Answer:
Light ray travels in a straight line.
Question 2.
Which objects allow light to pass through them?
Answer:
The objects that allow light to pass freely through them and through which objects can be seen clearly are called transparent objects.
Question 3.
What is the reflected ray of light?
Answer:
The ray of light that comes back after suffering reflection from a mirror is called reflected ray of light.
Question 4.
What is a shadow?
Answer:
An area of darkness formed by an opaque object obstructing light is called a shadow.
Question 5.
Define obstacles.
Answer:
An object which comes to the path of the light is called an obstacle.lt is the presence of obstacles in the path of light that results in shadow formation.
Question 6.
Define the following terms :
a) Luminous objects
b) Non-Luminous objects
Answer:
Luminous objects: The objects which emit light by themselves are called luminous objects. These objects can be natural or artificial. For example, Sun, the planets, etc. Non – Luminous objects: The objects which do not emit their own light but reflect the light of a luminous objects. These objects can be natural or artificial.For example, the moon, the planets, etc.
Question 7.
What is umbra ?
Answer:
Umbra is the darkest part of the shadow present in the middle of it, which forms due to the absence of light.
Question 8.
What is penumbra ?
Answer:
Penumbra is the faintest part of the shadow present at the corners of it. It is formed when the light is not completely blocked.
Question 9.
On which principle that a pinhole camera is based on ?
Answer:
A pinhole camera is based on the principle that the light travels in a straight line.
Question 10.
What do you mean by transparent objects ?
Answer:
Transparent objects are those that allow all light to pass through them fully, allowing one to see right through them. Transparent items include air, clear water, and cellophane tape.
Question 11.
What do you mean by translucent objects ?
Answer:
The objects that allow light to pass through them only partially is called a translucent objects.Translucent things include oiled paper, coloured glass panes, coloured solutions, and so forth. Example: Butter paper, tissue paper, etc.
Question 12.
What do you mean by opaque objects ?
Answer:
Opaque objects making them do not allow any light to flow through them at all. These items are impossible to see through. Opaque items include cardboard, metal, wood, and other materials.
Question 13.
Name some natural luminous bodies,
Answer:
Som natural luminous bodies are sun, stars, fire, fireflies.
Question 14.
Name the device which can be used to see things on the other side of a high wall.
Answer:
Periscope is used to see things on the other side of a high wall.
Question 15.
On which property of light a pinhole camera does work ?
Answer:
Pinhole camera works on the property of rectilinear propagation of light.
Short Answer Questions (3 Marks)
Question 16.
Moon is a non-luminous object. How does it shine at night ?
Answer:
Objects which do not emit light on their own are known as non-luminous objects. Moon does not emit its own light and therefore is a non-luminous object. But, we are able to see the Moon due to the reflection of Sun’s light from its surface.
Question 17.
What is a light ? What is the main source of light on the Earth ?
Answer:
Light is the form of energy which enables us to see the objects around us. Object which emits light, is called a source of light. The main source of light on the Earth is sun.
Question 18.
Differentiate between luminous and non-luminous body.
Answer:
Differences between luminous and non luminous body are as follows :
| S.No. | Luminous body | Non-Luminous body |
| 1. | The bodies which emit light on their own are called luminous bodies. | The bodies which do not emit light on their own are called non-luminous bodies. |
| 2. | Luminous objects are seen on their own. | Non-luminous objects are seen due to luminous objects. |
| 3. | They cause the sensation of light. | They do not cause the sensation of light. |
| 4. | Example: Sun, stars. | Examples: Moon, mirror. |
Question 19.
Name any four man-made sources of light.
Answer:
The man-made sources of light are:
- torchlight
- An electric build
- An oil lamp
- Candles
Question 20.
What are the essential conditions for the formation of shadows?
Answer:
The conditions for the formation of shadow are:
- There should be an opaque object in the way of light.
- There should be a source of light and screen
- The light rays falling on the opaque object is blocked by it.
Question 21.
If you are standing on the road and your friend throws a torchlight on your chest, will the shadow form at your back?
Answer:
To form a shadow we need not only a source of light, but also we need a screen, where it appears. There is a source of light, but there is no screen at the back, so the shadow will not form.
Question 22.
What is the lateral inversion ? Explain with the help of an example.
Answer:
When the image of an object is erect but is inverted in the lateral side, it is called lateral inversion. Example: Right side of the object appears as left side in the image.
Question 23.
What is a pinhole camera? How does it works?
Answer:
A pinhole camera is a device which forms a photograph-like image of a bright object on a screen. When the pinhole of the camera is turned towards a bright object a real inverted image of the object is formed on the screen.
Question 24.
How can a transparent glass sheet convert into a translucent sheet?
Answer:
There are numerous ways to convert a transparent glass sheet into translucent some of them are as follows:
- By applying a thin layer of oil, ghee, butter etc. on the glass sheet (this will allow the light to partially pass through the glass sheet).
- By covering a side of sheet by the butter paper and place it on the glass sheet.
- Rubbing the surface of the glass by some materials like (sand paper).
Question 25.
What is a mirror? What type of images are formed by it?
Answer:
The glass sheet having a polished, shiny, smooth and reflective surface on the other side is called a mirror. The image generated by a mirror is always imaginary, erect and laterally inverted.
Question 26.
What is reflection?
Answer:
When a ray of light falls on a smooth and shiny surface, the whole of light is sent back in the same medium. It is called reflection. Mirrors do not allow even a small amount of light to pass through them. Mirrors show regular and complete reflection.
Question 27.
Classify the following objects as luminous or non-luminous: Air, star, book, torch, lit matchstick, burning candle.
Answer:
| S.No. | Object | Luminous or Non – luminous |
| 1. . | Air | Non luminous |
| 2. | Star | Luminous |
| 3. | Book | Non luminous |
| 4. | Torch | Luminous |
| 5. | Lit matchstick | Luminous |
| 6. | Burning candle | Luminous |
Question 28.
Classify the following as transparent, translucent or opaque: Oiled paper, clear water, aluminium foil, cardboard, air, coloured glass plane.
Answer:
| S.No. | Object | Transparent, translucent or opaque |
| 1. | Oiled paper | Translucent |
| 2. | Clear water | Transparent |
| 3. | Aluminium foil | Opaque |
| 4. | Cardboard | Opaque |
| 5. | Air | Transparent |
| 6. | Coloured glass plane | Translucent ‘ |
Question 29.
On a sunny day, does a bird or an aeroplane flying high in the sky casts its shadow on the ground? Under what circumstances, can we see their shadow on the ground?
Answer:
No, it does not cast any shadow on the ground because it is very high in the sky. It can cast shadow only if it is at some lower height, i.e., if it is near to the ground, we can see its shadow.
Question 30.
Is air around us always transparent? Discuss.
Answer:
We can see the objects through air clearly means we can observe all the objects in their original shapes and sizes without any disturbance, it means the environment around us which is just air, must be transparent. But when thick smoke, thick clouds, etc., are present in the air, it does not remain transparent.
Long Answer Questions (5 Marks)
Question 31.
Write differences between shadow and image.
Answer:
Differences between shadow and image are as follows:
| S.No | Image | Shadow |
| 1. | It is formed by intersection of reflected rays. | Shadow is formed when no light is allowed to pass through the object. |
| 2. | Images can be seen When reflected light approaches observer’s eye. | No light enters the observer’s eyes. |
| 3. | Image gives more information such as colour, structure etc. | Shadow does not provide such information. |
| 4. | Image can be straight or inverted. | Shadow is never inverted. |
| 5. | Image formed by a plane mirror cannot be seen on a screen. | Shadow can be seen only on the surface. |
| 6. | Size of image in a plane mirror is always the same as that of the object. | Size of the shadow can be changed by changing the position of the object and source of light. |
Question 32.
On the basis of the passing of light through the object, what are the different types of objects? Explain them.
Answer:
On the basis of the passing of light through the object, the types of objects are:
- Transparent objects: The objects which allow the light to pass through them easily and through which we can seo clearly are known as transparent objects.
Examples: Air, clear water, and cellophane tape. - Translucent objects: The objects which allow light to pass through them partially and we cannot see clearly through them are called translucent objects.
Examples: Oiled paper, coloured glass panes, coloured solutions. - Opaque objects: The objects which do not allow the light to pass through them are called opaque
objects. Opaque items include cardboard, metal, wood, and other materials.
Examples: Books, bricks etc.
Question 33.
How can you prove that light reflects when it falls on a smooth surface?
Answer:
To prove the reflection of light, we need to put a mirror in a darkroom. Now, throw your light on it with the help of a torch. We would see that the rays of light which falls on the mirror bends towards another direction and lights up that place.
Example: A small valley town of Rjukan in Norway is surrounded by the high hills due to which the town is in dark for the almost half year in winter seasons. So, to resolve this issue, giant mirrors have been placed on the top of the hill to reflect the beam of light into the town during the dark winter months.
Question 34.
What is a shadow ? Write the characteristics of a shadow.
Answer:
The dark patch formed on the other side of the object, opposite to the light surface is called a shadow.
Characteristics of a shadow are:
- It is always black, regardless of the colour of the object used to make the shadow.
- The shadow of an object is formed on the opposite side of the light source.
- The position of the shadow changes with the position of the light source. This may be seen that as the position of the sun changes from morning to evening, the length and direction of the shadow also change.
- The thickness of a shadow is generally determined by the separation or range between the item as well as the light source.
- The size of a shadow varies depending on the distance between the object and the source of light, and the distance between the object and the screen.
Question 35.
What is a mirror? Explain its functioning.
Answer:
1. Mirror is a smooth, shiny surface which reflects light rays to form a clear image of an item.
2. It is made up of glass with a mirror coating on one side.
3. The image formed in the mirror is created by the reflecting of light rays off the surface of the mirror.
4. The light rays coming from the object hits the mirror and bounce off at an angle.
5. The image of the object in the mirror is created by the reflection of light rays. Reflections cause the images generated to be laterally inverted.
Question 36.
Explain the construction, working and application of pinhole camera.
Answer:
Aim: Preparing a pinhole camera
Materials required: Two shoe boxes, A tooth pick, A translucent paper, Tape, Scissor, A sharp knife, Pencil.
Procedure:
1. Take two boxes so that one can slide into another with no gap in between them. Cut open one side of each box.
2. On the opposite face of the larger box, make a small hole in the middle.
3. In the smaller box, cut out from the middle a squre with a side of about 5 to 6cm.
4. Cover this open square in the box with tracing paper (translucent screen).
5. Slide the smaller box inside the larger one with the hole. In such a way that the side with the tracing paper is inside.
6. Now it is ready to use.
7. Hold the pinhole camera look through the open face of the smaller box.
8. You should use a piece of black doth to cover your head and the pinhole camera.
9. Now focus on the object you want to capture in the camera.
10. Make sure that the objects you wish to look at through your pinhole camera are in bright sunshine.
11. Move the smaller box forward or backward till you get a picture on the tracing paper pasted at the other end.
Question 37.
Explain that light has the property of rectilinear propagation with the help of an activity.
Answer:
1. We take three pieces of cardboard.
2. Place them one on the top of one another and make a hole in the middle of each cardboard by using a thick nail.
3. Erect these cards up on the table at a short distance away from each other. Take a candle which is of the same height as the holes in the cards. Light the candle and place it in front of the cards.
4. We see that the light of candle is visible only when the holes on cards lie in a straight line.
5. If we disturb them the light of candle disappears. This experiment shows that light propagates in a straight line.
Question 38.
A sheet of plywood, a piece of muslin cloth and that of a transparent glass, all of the same size and shape were placed at A one by one in the arrangement shown in figure. Will the shadow be formed in each B case? If yes, then how will the shadow on the screen be different in each case? Give reasons for your answer.
Answer:
Yes, the shadow will be formed in each case but in all the cases, the darkness of the shadow will be different.
- Most of the light in case of transparent sheet of glass will pass through the glass. So, the darkness of shadow will be very low.
- Most of the light in case of muslin cloth will be reflected. So, the shadow will be darker than the transparent sheet of glass.
- While in case of plywood, all the light would be stopped completely by the playwood. So, the darkness strength will be highest in this case.
Case Based Questions (4 Marks)
1. Prasanna’s teacher asked to make a pinhole camera by themselves. Prasanna read the activity given in the textbook on how to make a pinhole camera. But she was unable to get the image of a well lit object. She was very upset. Her elder sister on observing her pinhole camera found that the hole made by her was quite large. She rectified Prasanna’s mistake and helped her making that another pinhole camera. Now, Prasanna can see the image of the object.
Now answer the following the questions.
a) On which principle of light does a pinhole camera work?
Answer:
Pinhole camera works on the principle of rectilinear propagation of light.
b) Why was Prasanna unable to get the image of a well lit object?
Answer:
She made large hole instead of fine hole.
c) How does the formation of the image by a pinhole camera is affected by the size of the hole?
Answer:
The finer will be the hole the sharper will be the image formation and vice versa.
d) What values of Prasanna is shown here?
Answer:
Prasanna got upset easily without looking and inspecting the actual case, she is bit careless in doing this activity.