Question 11 Mark
Why we cannot see our image in the mirror in complete dark room?
Answer
View full question & answer→We cannot see our image in the mirror in complete dark room because there is no light to reflect.
Questions
[1 Marks Each] QUE - ANS
Take a timed test
65 questions · self-marked practice — reveal the answer and mark yourself.
Question 21 Mark
What is an obstacle?
Answer
View full question & answer→An object which comes to the path of light is called an obstacle.
Question 31 Mark
Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
Answer
Opaque objects make shadows.
View full question & answer→Opaque objects make shadows.Question 41 Mark
Activity.Fix a comb on one side of a large thermocol sheet and fix a mirror on the other side as shown in the figure. Spread a dark-coloured sheet of paper between the mirror and the comb. Keep this in sunlight or send a beam of light from a torch through the comb.
What do you observe? Do you get a pattern similar to that shown in figure?
What do you observe? Do you get a pattern similar to that shown in figure?
Answer
View full question & answer→Light travels in straight line and gets reflected from the mirror. Yes, we get a pattern similar to that shown in the figure.
Question 51 Mark
What do we need in order to see a shadow?
Answer
View full question & answer→We need
- A source of light,
- An opaque object in the way of light, and
- A screen;
Question 61 Mark
Does the direction of shadow change during the day? Does the length of shadow also change from season to season?
Answer
View full question & answer→Yes, the direction of shadow changes as the sun changes its position during the day. The length of the shadow also changes from season to season.
Question 71 Mark
Write down four man-made sources of light.
Answer
View full question & answer→- Candle.
- Oil lamp.
- Electric bulb.
- Torch.
Question 81 Mark
A student observes a tree given in Fig. through a pin hole camera. Which of the diagrams given in Fig. $(a)$ to $(d)$, depicts the image seen by her correctly?
Answer
Explanation:
Option $(d)$ is the correct image seen by her because a pinhole camera always forms upside down (i.e. inverted) image.
View full question & answer→Explanation:
Option $(d)$ is the correct image seen by her because a pinhole camera always forms upside down (i.e. inverted) image.
Question 91 Mark
How are moon and planets visible to us, though they are not luminous?
Answer
View full question & answer→Because they reflect light from the sun.
Question 101 Mark
What are transparent objects?
Answer
View full question & answer→Those objects which allow light rays to pass through them completely are called transparent objects. One can see clearly through these objects.
Question 111 Mark
What is umbra and penumbra?
Answer
View full question & answer→Umbra is the dark region behind object facing light which does not receive light at all.
Penumbra is the less dark part of shadow. It is the outer part of shadow.
Penumbra is the less dark part of shadow. It is the outer part of shadow.
Question 121 Mark
On what factor does the proportion of light that enters an object depend?
Answer
View full question & answer→Optical nature of the object.
Question 131 Mark
How will you convert a transparent glass sheet into a translucent sheet? Suggest any two ways to do it.
Answer
View full question & answer→By smearing a thin layer of oil we may convert a transparent glass sheet into a translucent sheet.
By covering one side of the glass sheet by butter paper.
By covering one side of the glass sheet by butter paper.
Question 141 Mark
Give two example of luminous object.
Answer
View full question & answer→Sun and torch bulb.
Question 151 Mark
Fill in the blanks with appropriate words:
In a plane mirror, our left hand looks like right hand. This phenomenon is called ______.
In a plane mirror, our left hand looks like right hand. This phenomenon is called ______.
Answer
View full question & answer→In a plane mirror, our left hand looks like right hand. This phenomenon is called lateral inversion.
Question 161 Mark
Why is the moon not considered as a luminous body?
Answer
View full question & answer→Moon is a non-luminous body because it shines by reflecting the sunlight falling on it.
Question 171 Mark
Give two examples of non luminous objects.
Answer
View full question & answer→Chair and shoe.
Question 181 Mark
What type of object is said to be transparent?
Answer
View full question & answer→If we are able to see clearly through an object, it is said to be transparent.
Question 191 Mark
What is reflection?
Answer
View full question & 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 201 Mark
What is the path of light?
Answer
View full question & answer→Straight line.
Question 211 Mark
What are luminous and non-luminous objects?
Answer
View full question & answer→Luminous objects: Objects that give out or emit light of their own, e.g., sun, torch, light, bulbs, etc.
Non-luminous objects: Objects that do not give out light of their own, e.g., the moon, chair, shoe, pen, etc.
Non-luminous objects: Objects that do not give out light of their own, e.g., the moon, chair, shoe, pen, etc.
Question 221 Mark
Define eclipse.
Answer
View full question & answer→Eclipse is a shadow formed in space that makes the sun or the moon invisible for some time.
Question 231 Mark
What are translucent objects?
Answer
View full question & answer→There are some objects through which we can see but not clearly. Such objects are known as translucent objects.
Question 241 Mark
Can you think of a situation where we can see the path of the light?
Answer
View full question & answer→In a dark room, we can see with torch light which goes straight. Similarly, dust particles become visible when light enters the room through fine hole.
All these examples indicate that light travels in straight line.
All these examples indicate that light travels in straight line.
Question 251 Mark
Why is the image formed in a pinhole camera inverted?
Answer
View full question & answer→In a pinhole camera, image formed is inverted because the object is between radius of curvature and focus.
Question 261 Mark
Does the fire emit light?
Answer
View full question & answer→Yes, fire emits light.
Question 271 Mark
Why do we need a shiny surface for reflection?
Answer
View full question & answer→The extent of reflection depends upon the shine and smoothness of the surface. More is the shine and smoothness of the surface, more will be the reflection. That is why mirrors reflect most of the light falling on it. Hence, for reflection, shiny surfaces are required.
Question 281 Mark
Define ‘Mirror’.
Answer
View full question & answer→A smooth shining surface, which rebounds the light back in same or in different direction is called a mirror.
Question 291 Mark
Why is silvered glass used as a mirror?
Answer
View full question & answer→The silvered glass has a smooth surface and the smoothness helps in forming clear image. Silvering makes it shiny and the shiny surface helps in reducing the absorption.
Question 301 Mark
Why we should not look directly at sun?
Answer
View full question & answer→We should not look directly at sun because that could be extremely harmful for the eyes.
Question 311 Mark
Why we cannot see objects through $T$ shaped or $N$ shaped pipe?
Answer
View full question & answer→We cannot see objects through $T$ shaped or $N$ shaped pipe because light travels through straight line.
Question 321 Mark
Give two examples of opaque objects.
Answer
View full question & answer→Plastic box and wooden table.
Question 331 Mark
Fill in the blanks with appropriate words:
Light travels in a ______.
Light travels in a ______.
Answer
View full question & answer→Light travels in a straight line.
Question 341 Mark
Which of these object can cast shadow.
Paper, air, rock, glass, sun.
Paper, air, rock, glass, sun.
Answer
View full question & answer→Paper, rock and sun.
Question 351 Mark
Define screen.
Answer
View full question & answer→Screen is a surface on which images are formed.
Question 361 Mark
What do we need to see an object?
Answer
View full question & answer→To see an object, we need source of light, eyes and object. When light emitted by luminous body falls on an object, it is reflected back and received by our eyes. Then we see that object.
Question 371 Mark
Give two examples of transparent objects.
Answer
View full question & answer→Glass and water.
Question 381 Mark
Why is the shadow of an aeroplane flying high in the sky not seen on the ground?
Answer
View full question & answer→This is because the size of a flying aeroplane is very small with respect to the ground.
Question 391 Mark
If moon is non luminous, how it appears bright in night?
Answer
View full question & answer→Moon appears bright in night because it reflects sun light that falls on it.
Question 401 Mark
What type of objects does not cast shadow and why is that?
Answer
View full question & answer→Transparent and some translucent objects do not cast shadow because light passes through them.
Question 411 Mark
Shadows are of two kinds. What are they?
Answer
View full question & answer→Umbra and penumbra.
Question 421 Mark
Define pinhole camera.
Answer
View full question & answer→It is a device which forms a photograph like image of a bright object on a screen.
Question 431 Mark
Give examples of two substances through which light does not pass?
Answer
View full question & answer→Wood and bricks are the substances through which light does not pass.
Question 441 Mark
Fill in the blanks with appropriate words:
Shadow is _____.
Shadow is _____.
Answer
View full question & answer→Shadow is three dimensional.
Question 451 Mark
Sometimes, you are able to see the Sun or the Moon behind the clouds. What can you say about the ability of such clouds to transmit light?
Answer
View full question & answer→We may say that clouds behave as translucent object.
Question 461 Mark
When are shadows formed?
Answer
View full question & answer→Shadows are formed when an opaque object comes in path of light.
Question 471 Mark
Moon is a non-luminous object. How does it shine at night?
Answer
View full question & answer→Moon reflects the light of the sun at night.
Question 481 Mark
Look at the figure given in Fig.
Will there be any difference in the shadow formed on the screen $A$ and $B$?
Will there be any difference in the shadow formed on the screen $A$ and $B$?
Answer
View full question & answer→No, there will not be any difference because the length and breadth of an object are same in both the cases.
Question 491 Mark
Why polished surface cause glares in our eyes?
Answer
View full question & answer→Polished surface cause glares in our eyes because they produce regular reflection of light.
Question 501 Mark
What are luminous objects?
Answer
View full question & answer→Objects that give out or emit light of their own are known as luminous objects.
Question 511 Mark
What happens when light falls on a mirror?
Answer
View full question & answer→Mirror is silvered on one side, so it does not allow the light to pass through it. It reflects almost whole of the light falling on it.
Question 521 Mark
Define luminous body.
Answer
View full question & answer→The objects which emit light of their own are called luminous bodies, e.g., the sun, the stars, etc.
Question 531 Mark
Close your eyes while looking towards bright sunshine. Now, cover the eyes with your palm still keeping them closed. Do you notice any difference? On the basis of this experience, state whether your eyelids are transparent, translucent or opaque.
Answer
View full question & answer→On the basis of the experience, we observe our eyelids are opaque.
Question 541 Mark
List four natural sources of light.
Answer
View full question & answer→- Sun.
- Stars.
- Fire.
- Jugnu (Firefly).
Question 551 Mark
How can a transparent sheet be converted into a translucent sheet?
Answer
View full question & answer→By greasing the paper with oil or fat.
Question 561 Mark
What change in the path of light takes place when light falls on a shiny surface? What is this called?
Answer
View full question & answer→The light comes back in the same plan when light falls on a shiny surface. This is known as reflection of light.
Question 571 Mark
Name sources of light that are not hot.
Answer
View full question & answer→Tube light, jugnu.
Question 581 Mark
What materials can be used to make a pinhole camera? How can it be used?
Answer
View full question & answer→Pinhole camera can be made with simple material like cardboard, tracing paper etc. It can be used to image the sun and brightly lit objects.
Question 591 Mark
What are the three things required for the formation of shadows?
Answer
View full question & answer→Light, space and opaque object.
Question 601 Mark
What do you mean by scattering of light?
Answer
View full question & answer→When a beam of light falls on a rough surface, it is turned back in different directions, it is called scattering of light.
Question 611 Mark
Why is shadow formed when an opaque object comes in path of light?
Answer
View full question & answer→Light travels in a straight line and when opaque object obstructs it, shadow is formed.
Question 621 Mark
Classify the following into transparent, opaque and translucent objects:
Wax, spectacles, a heap of salt, a stone, dense smoke, wood, skin, balloon, rubber, membrane of a tabla, blood and milk.
Wax, spectacles, a heap of salt, a stone, dense smoke, wood, skin, balloon, rubber, membrane of a tabla, blood and milk.
Answer
View full question & answer→Transparent objects are Spectacles.
Opaque objects are A stone, wood, a heap of salt, dense smoke, and membrane of tabla.
Translucent objects are Blood, milk, wax, skin, balloon, rubber.
Opaque objects are A stone, wood, a heap of salt, dense smoke, and membrane of tabla.
Translucent objects are Blood, milk, wax, skin, balloon, rubber.
Question 631 Mark
What is periscope?
Answer
View full question & answer→Optical object by which we can see objects located above our line of sight.
Question 641 Mark
Define opaque objects with example.
Answer
View full question & answer→Those materials which do not allow light to pass through them, are called opaque objects. Examples wood, stone, etc.
Question 651 Mark
Whether a shadow is two-dimensional or three-dimensional?
Answer
View full question & answer→Shadow is not just the two-dimensional outline that you see on the ground. All the space behind the opaque object up to some distance behind it seems to be filled with the shadow.
