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Ncert Exemplar Solutions Class 7 Science Light
Welcome to NCTB Solutions. Here with this post we are going to help 7th class students for the Solutions of NCERT Exemplar Class 7 Science Book, Unit 15, Light. Here students can easily find step by step solutions of all the problems for Light, Also here our Science teacher’s are solved all the questions with easily understandable language with proper guidance so that all the students can understand easily.
Light all Question Solutions :
Multiple Choice Questions :
Question no – (1)
Boojho and Paheli were given one mirror each by their teacher. Boojho found his image to be erect and of the same size whereas Paheli found her image erect and smaller in size. This means that the mirrors of Boojho and Paheli are, respectively
Answer :
The correct answer is option – (c)
This means that the mirrors of Boojho and Paheli are, plane mirror and convex mirror respectively.
Question no – (2)
Which of the following can be used to form a real image?
Answer :
The correct option is – (a)
Only Concave mirror can be used to form a real image.
Question no – (3)
If an object is placed at a distance of 0.5 m in front of a plane mirror, the distance between the object and the image formed by the mirror will be
Answer :
The appropriate answer is option – (b)
The distance between the object and the image formed by the mirror will be 1 m.
Question no – (4)
You are provided with a concave mirror, a convex mirror, a concave lens and a convex lens. To obtain an enlarged image of an object you can use either
Answer :
The answer is option – (b)
To obtain an enlarged image of an object you can use either concave mirror or convex lens.
Question no – (5)
A rainbow can be seen in the sky
Answer :
The correct answer is alternative – (b)
A rainbow can be seen in the sky when the sun is behind you.
Question no – (6)
An erect and enlarged image can be formed by
Answer :
The answer is alternative – (b)
An erect and enlarged image can be formed by only a concave mirror.
Question no – (7)
You are provided with a convex mirror, a concave mirror, a convex lens and a concave lens. You can get an inverted image from
Answer :
The correct answer is option – (c)
You can get an inverted image from both concave mirror and convex lens.
Question no – (8)
An image formed by a lens is erect. Such an image could be formed by a
Answer :
The correct option is – (b)
Such an image could be formed by a concave lens provided the image is smaller than object.
Very Short Answer Questions :
Question no – (9)
Answer :
The lens are concave because concave lens forms images which are always virtual, erect and smaller in size for an object kept at different positions in front of it.
Question no – (10)
Answer :
(a) The inner surface of a steel spoon acts as a Concave mirror.
(b) The outer surface of a flat steel plate acts as a Plane mirror.
(c) The outer shining surface of a round bottom steel bowl acts as a Convex mirror.
(d) The inner surface of the reflector of a torch acts as a Concave mirror.
Question no – (11)
Answer :
(a) A concave lens can be used to produce an enlarged and erect image
This statement is False.
Reason : A concave lens can be used to produce a diminished image and erect image.
(b) A convex lens always produces a real image
This statement is False.
Reason : A convex lens can form a real as well a virtual image.
(c) The sides of an object and its image formed by a concave mirror are always interchanged
This statement is True.
(d) An object can be seen only if it emits light
This statement is False.
Reason : A object can be seen when it’s reflect the light that’s falling in it.
Short Answer Questions :
Question no – (12)
Answer :
A convex mirror is used as a side mirror in a scooter as it will form a diminished image of the large area that is behind him. So he will be more aware of the surrounding around behind him and drive cautiously.
Question no – (13)
Answer :
The nature of lens A : The lens A is a convex lens as the rays of light that are passing through it are clearly converging or moving towards each other.
The nature of lens B : The lens B is a concave lens as the rays of light that are passing through it are clearly diverging or moving away from each other.
Question no – (14)
Answer :
Boojho will not be able to observe band of seven colours because since laser light are monochromatic that is they are made up of only one colour so it will not split into seven colors.
Question no – (15)
Answer :
The correct sequence (1-7) of colours in the spectrum formed by the prisms A and B are –
| The prisms A : | The prisms B : |
| (1) Red | (1) Violet |
| (2) Orange | (2) Indigo |
| (3) Yellow | (3) Green |
| (4) Blue | (4) Blue |
| (5) Green | (5) Yellow |
| (6) Indigo | (6) Orange |
| (7) Violet | (7) Red |
Question no – (16)
Answer :
As the side mirror of the scooter has been replaced with a plane mirror. The driver will face much difficultly in driving as we know that convex mirrors are very efficient in showing a diminished image of the area that is behind him but a simple mirror is not efficient at that.
Question no – (17)
Answer :
The rusted torch will not be able to properly emit a beam of high intensity light.
Question no – (18)
Answer :
An erect and enlarged image of the object can be formed on the screen with the following arrangement. First of all we need to keep the the concave mirror, the object and the screen in a straight line, in the given order. The object should be kept at a distance of about 50 cm in front of the mirror. We then have to slightly bring the screen close to the object till a sharp image of the object forms on the screen. In this way we could form an erect and enlarged image of the desired object.
Question no – (19)
Answer :
In order to identify the type of lens we must notice the size of the letters. If the letters of the newspaper are small or diminished then it’s a concave lens but if the size of the letter are small then it’s a convex lens.
Question no – (20)
Answer :
The shopkeeper must fix a convex mirror in his shop because he needs a mirror which will give a wide view of his shop so a convex mirror will form images of a large area of his shop.
Question no – (21)
Answer :
As the image formed on the screen by the convex lens keep on decreasing it is probably happening because the distance between the lens and object is increasing.
Long Answer Questions :
Question no – (22)
Answer :
The two possible ways of getting a real image of a distant tree are
(i) A real image of the tree can be formed by using a concave mirror, for this we need to align the concave mirror, the vertically placed screen and the tree in a straight line as per the given order. After that we must adjust the distance between the mirror and the screen till we get a clear image of the distant tree in the screen.
(ii) A real image of a tree can be formed by using a convex lens, for this we need to align a vertically placed screen, a lens and a tree in a straight line as per the given order. After that we need to adjust the distance between the lens and the screen till we get a clear image of the tree on the screen.
Question no – (23)
Answer :
This is a convex lens because it is the property of a convex lens to keep on increasing the size of the image as the distance between the object and the lens decreases
No, if we keep on decreasing the distance between the lens and object then it will not form a image on the screen but will form a virtual image of the object.
Question no – (24)
Answer :
The three mirrors could be identified by noticing the image formed by the mirrors :
(i) If the image formed by the mirror is erect, virtual and of the same size as the object then it’s a plane mirror.
(ii) If the image formed by the mirror is virtual, erect and diminished then it’s a convex mirror.
(iii) If the image formed by the mirror is real or virtual, diminished or enlarged or inverted or erect depending on the position of object then it’s a concave mirror.
OR
The three mirrors can be identified by noticing the shape of the mirrors :
(I) If the reflecting surface of the mirror is straight then it is a plane mirror.
(II) If the reflecting surface of the mirror is bent inwards then it’s a concave mirror.
(III) If the reflecting surface of the mirror bus bent outwards then it’s a convex mirror.
Other Chapter Solutions :
👉 Heat
👉 Physical and Chemical Changes
👉 Weather, Climate and Adaptation of Animals to Climate
👉 Soil
👉 Transportation in Animals and Plants
👉 Electric Current and Its Effects
👉 Wastewater Story
