Students rely on Class 7 Science Extra Questions and Class 7th Curiosity Chapter 11 Light Shadows and Reflections Important Extra Question Answer to improve their grades.
Class 7 Science Chapter 11 Light Shadows and Reflections Extra Questions
Class 7 Science Chapter 11 Extra Questions on Light Shadows and Reflections
Light Shadows and Reflections Class 7 Very Short Question Answer
Question 1.
Does a shadow show all the details of the object?
Answer:
No. It shows only the shape of the object.
Question 2.
Can you see your reflection in the water of your swimming pool? Why?
Answer:
Yes. It is because the surface of water reflects the light.
Question 3.
Juhi was sitting in her drawing room enjoying the activities of the squirrels in her garden. The doors and windows of the room were closed. Can you tell the material from which the door is made up of?
Answer:
The door is made up of glass. Glass is a transparent material.
Question 4.
Suggest a situation where we obtain more than one shadow of an object at a time.
Answer:
When light falls on an object from more than one source, we get more than one shadow of that object.
Question 5.
Mehak wants to perform a shadow show in her classroom. What are the requirements for her show?
Answer:
For the shadow show, she requires a source of light, opaque screen objects or puppets, a translucent screen, a dark room, and movement and story telling.
Question 6.
What type of objects do not cast shadow and why is that?
Answer:
Transparent and some translucent objects do not cast shadow because light passes through them.
Question 7.
Can a completely transparent object cast a shadow?
Answer:
No, transparent objects do not typically cast shadows. Shadows are formed when an object obstructs light and prevents it from reaching a surface. Because transparent objects allow light to pass through them, they don’t block light in the same way opaque objects do, resulting in no shadow formation.
Question 8.
Explain how, we are able to see the table lying in a room though it does not give out its own light.
Answer:
We see a table in a room even though it doesn’t produce its own light because of reflection. Light from a source like a lamp or the sun illuminates the room, and the table reflects that light. This reflected light travels to our eyes, allowing us to perceive the table.
Question 9.
State one property of light which is demonstrated by the working of a pinhole camera.
Answer:
The primary property of light demonstrated by a pinhole camera is its rectilinear propagation, meaning light travels in straight lines.
Light Shadows and Reflections Class 7 Short Question Answer
Question 1.
Why is the Moon considered as a non-luminous body?
Answer:
The Moon is a non-luminous object. It does not emit its own light. It just reflects the light emitted by the Sun that falls on it.
Question 2.
State difference between transparent and translucent objects with examples.
Answer:
If we are able to see clearly through an object, it is said to be transparent. Whereas there are some objects through which we can see but not clearly. Such objects are known as translucent objects.
Transparent objects allow light to pass through them completely whereas translucent objects allow light to pass through them only partially.
Examples: Transparent: Clear glass, Water, Air etc.
Translucent: Frosted glass, Butter paper etc.
Question 3.
In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror? Why?
Answer:
When we hold up a mirror in front of us in a completely dark room, we do not see our reflection in the mirror. This is because a source of light is required to see the reflection.
Question 4.
Differentiate between transparent and opaque materials.
Answer:
| Transparent objects | Opaque objects |
| These objects allow light to pass through them. | These objects do not allow light to pass through them. |
| These objects do not form shadow in presence of light. | These objects form shadows in presence of light. |
| Examples: glass, water | Examples: wood, stone, brick |
Question 5.
A student covered a torch with a red cellophane sheet to obtain red light. Using the red light, she obtains a shadow of an opaque object. She repeats this activity with green and blue light. Will the colour of the light affect the shadow? Explain.
Answer:
The colour of the light will not affect the shadow, because shadow is the dark patch formed when an object obstructs the path of light and hence no light reaches in the shadow region.
Question 6.
What materials can be used to make a pinhole camera? How can it be used?
Answer:
Pinhole cameras can be made with simple materials like two cardboard boxes and a small piece of tracing paper etc. It can be used to capturing images of brightly lit objects and images of the Sun.
Question 7.
Observe the picture given in Fig. A sheet of some material is placed at position (P’, still the patch of light is obtained on the screen. What is the type of material of this sheet? (NCERT Exemplar)
Answer:
A sheet of transparent material is placed at P
Question 8.
You are given a transparent glass sheet. Suggest any two ways to make it translucent without breaking it. (NCERT Exemplar)
Answer:
(i) By applying oil, grease, butter on it or pasting a butter paper on it.
(ii) Grinding (rubbing) the surface of the glass by any abrasive material.
Question 9.
A football match is being played at night in a stadium with flood lights ON.
You can see the shadow of a football kept at the ground but cannot see its shadow when it is kicked high in the air. Explain. (NCERT Exemplar)
Answer:
We can see the shadow of football lying on the ground because the ground acts as a screen for it. However, when the football is kicked high, the ground, which is acting as a screen, is away from the football, hence no shadow of the football will be formed on the ground.
Light Shadows and Reflections Class 7 Long Question Answer
Question 1.
Give the meaning of the term Lateral inversion. Suggest how it may be used to send a ‘coded (secret)’ message.
Answer:
Lateral inversion is the phenomenon where a mirror image appears reversed, with left and right sides interchanged. This reversal can be used to send a coded message by writing the message normally, reversing the order of the letters, and having the recipient view the reversed message in a mirror.
Question 2.
Does the size of the shadow, of a given object, change even when there is no change in the source of light? Give one example in support of your answer.
Answer:
Yes, the size of a shadow can change even when the light source remains constant due to following reasons:
- Distance from the Light Source: As the object moves closer to the light source, the shadow appears larger because more light rays are blocked by the object to form a larger shadow on the surface. Conversely, as the object moves away from the light source, the shadow becomes smaller.
- Angle of Light: The angle at which the light strikes the object also affects the shadow’s size. When light hits the object at a steeper angle, the shadow appears smaller. At a more shallow angle, the shadow becomes larger.
Question 3.
Write any five differences between shadow and reflection formed by a plane mirror.
Answer:
| Reflection formed by a Plane Mirror | Shadow |
| Identifies the object and gives its complete information. | Does not necessarily identify the object and also give complete information about the object. |
| Reflection is as colourful as the object is. | Irrespective of the colours of the object, the shadow is always black. |
| Reflection cannot be obtained on a screen | A shadow is always formed on a screen. |
| Reflection shows lateral inversion. | The phenomenon of lateral inversion is not observed in case of shadow. |
| Reflection of a given object, in a plane mirror, has a fixed size, irrespective of its distance from the mirror. | The size of the shadow of a given object changes with a change in distance between the object and the source of light. |
Question 4.
How will you make a simple pinhole camera?
Answer:
Construction of Pinhole Camera: Take two cylindrical cardboard tubes one having a smaller diameter than the other. Cover one of the open sides of the smaller tube with a butter paper. Use an aluminium foil over one of the openings of the larger tube so as to completely cover it. With the help of a sharp needle, make a clean hole in the centre of the aluminium foil. Slide the smaller tube into the larger one and keep the foil and the butter paper sides outwards. The pinhole camera is now ready for use.
Put the camera on a suitable base (or just hold it in hand) so that the hole, in the aluminium foil, is facing some well-illuminated distant object. Slide the smaller tube back and forth until you see a clear image of the object on the screen (butter paper).
Light Shadows and Reflections Class 7 Case Based Questions
Question 1.
When we pass under a tree having a large number of leaves, we observe small round spots of light in the shadow of the tree. These round spots, in fact, are pinhole images of the Sun. The gaps between the leaves act as pinholes. These gaps between the leaves are of irregular shapes, but we can see circular images of the Sun. This is a natural pinhole camera.
(i) What acts as pinholes in this natural pinhole camera?
Answer:
The gaps between the leaves act as pinholes in this natural pinhole camera.
(ii) Write one use of a pinhole camera.
Answer:
It can be used to see some distant objects like trees or a building.
(iii) When the size of the pinhole in a pinhole camera is bigger, what type of image is formed?
Answer:
Diffused or blurred image of an object is formed.
Question 2.
A kaleidoscope is a tubeshaped optical device that uses mirrors and coloured glass or plastic pieces to create symmetrical patterns through repeated reflections. The angle between the mirrors determines the number of times an object’s reflection is repeated, resulting in unique patterns that never appear again.
(i) What is the primary principle behind a kaleidoscope?
Answer:
Reflection (Although it’s a combination of reflection and symmetry)
(ii) What creates the colourful patterns in a kaleidoscope?
Answer:
The colourful patterns are created by loose fragments of coloured glass or other materials that move and reflect light inside the kaleidoscope.
(iii) Describe the components of a kaleidoscope and their roles.
Answer:
A kaleidoscope typically consists of:
- Mirrors: Create symmetry and reflection
- Glass fragments or other materials: Create colourful patterns
- Rotation mechanism: Allows the user to rotate the device and change patterns.
Question 3.
Light enables us to see objects around us. An object which emits light is called a source of light.
For example, sun, torch, etc. An object which comes into the path of the light is called an obstacle. All the opaque objects seem to form a dark shadow of their own. We need a source of light, an opaque object in the way, and a screen to see a shadow.
(a) What enables us to see thinks around us?
Answer:
Light enables us to- see things around us.
(b) List some examples for sources of light.
Answer:
Sun, star, bulb, candle, match stick etc.
(c) Name any two non-luminous objects?
Answer:
Moon, planets. . .
Light Shadows and Reflections Extra Questions for Practice
Very Short Answer Type Questions
Question 1.
Mention the type of image.
(a) which can be formed on the screen.
(b) which cannot be formed on the screen.
Question 2.
On a sunny day, two identical bedsheets, of red and green colour, are hanging on a clothesline. What would be the colour of the shadows of these two bed sheets?
Question 3.
State the type of path that light ordinarily follows when going from one point to another?
Question 4.
State the characteristics of the image formed by a plane mirror.
Question 5.
When an opaque object comes closer to the source of light, will the size of shadow increase or decrease?
Question 6.
When does a shadow form?
Short Answer Type Questions
Question 1.
David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then find out the distance between David and his image.
Question 2.
Classify the materials given below as opaque, transparent or translucent. Air, smoke, fog, aluminium sheet, wooden board, cellotape, polythene sheet, lime juice, wax, rubber, tyre and milk.
Question 3.
State difference between transparent and translucent objects with examples.
Question 4.
What are the essential conditions for the formation of a shadow?
Long Answer Type Questions
Question 1.
Cover the face of a torch with transparent coloured paper. Send its beam through an opaque object. What do you observe?
Question 2.
Raghav set up the following arrangement in the science laboratory. He put
(i) a steel glass
(ii) a transparent glass, at the position P, one by one. Would a shadow be formed in each case? Give reason for your answer.
Question 3.
With the help of a diagram, show the formation of an image by a pinhole camera.
Case/ Source Based Questions
Question 1.
The periscope is a device which gives us a higher view than normal. By using a periscope, we can see the objects on the , other side of a high wall, without having to climb over the wall. It can also be used to see over the heads of the crowd (say, in a football match). A soldier sitting in a trench can observe the enemy activities above the ground by using a periscope.
(i) How many plane mirrors does periscope use ?
(ii) On what principle does this device work ?
(iii) Write any two uses of periscope other than mentioned in the paragraph.
Question 2.
Aditya was provided with butter paper, a clear glass sheet, and paper painted with black acrylic paint by his teacher to study their properties. Aditya first observed a source of light through three sheets of paper.
These were:
- Sheet 1: Butter paper
- Sheet 2: A clear glass
- Sheet 3: Paper painted with black acrylic paint.
(i) Which of the sheets will allow the light to pass through it completely?
(ii) Which of the sheets will form the darkest shadow when placed in front of a light source?
(iii) Will a butter paper allow light to pass through it completely?
Multiple Choice Questions (MCQs)
Choose the correct option in the following questions:
Question 1.
The ‘something’, which can change its shape and size, and may appear and disappear anywhere/anytime, is known as a
(a) image
(b) beam of light
(c) shadow
(d) reflector of light
Question 2.
The image, formed by a pinhole camera, is:
(a) erect and diminished
(b) inverted and enlarged
(c) inverted and diminished
(d) erect and enlarged
Question 3.
The image formed by a plane mirror is
(a) upright
(b) virtual
(c) same size as object
(d) all of the above
Question 4.
What happens to the size of a shadow when the object is moved closer to the light source?
(a) Increases
(b) Decreases
(c) Remains the same
(d) Disappears
Question 5.
The distance, between the object and its image, in a plane mirror is 6 m. If the object moves 1 m towards the mirror, then the (new) distance between the object and its image will be
(a) 5 m
(b) 6 m
(c) 4 m
(d) 8 m
Assertion-Reason Questions
Assertion-Reason (2) answer with explanation.
Directions: Each of the questions (i) and (ii) contain two statements – first ‘Assertion’ and second ‘Reason’. Select the correct answer to these question from the codes (a), (b), (c) or (d) as given below:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true and Reason is NOT the correct explanation of Assertion.
(c) Assertion is true and Reason is false.
(d) Assertion is false and Reason is true.
(i) Assertion (A): Light travels in a straight line.
Reason (R): Transparent objects allow all the light to pass through them.
(ii) Assertion (A): Shadows change shape when the object moves.
Reason (R): Shadows change colour when colour of the object changes.
Fill in the Blanks
(i) Objects, like the sun, which emit light of their own, are called _____
(ii) Light helps us to _____ objects.
(iii) The image formed in water is _____.
(iv) To increase the size of the shadow, move the object _____ the source.
(v) We cannot see clearly through a butter paper because it allows light to pass through it _____.
True or False
State whether True or False answer with reason:
(i) Light travels in curve path.
(ii) Mirror does not change the direction of light that falls on it.
(iii) The image of red rose and yellow rose is black in colour.
(iv) Chair is a luminous object.
(c) Materials that allow all light falling on them to pass through are called translucent.
Match the following:
Question 1.
Match the following items given in Column A with that in Column B:
| Column A | Column B |
| (a) Image | (i) Formed when an object blocks light |
| (b) Frosted glass | (ii) Plane mirror |
| (c) Shadow | (iii) Reflection |
| (d) Virtual image | (iv) Translucent material |
Question 2.
Match the following items given in Column A with that in Column B:
| Column A | Column B |
| (a) Opaque object | (i) Image |
| (b) Sun | (ii) Non-luminous |
| (c) Mirror | (iii) Shadow |
| (d) Moon | (iv) Translucent |
| (e) Frosted glass | (v) Luminous |