Multiple Choice Questions.............
Question 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
(a) plane mirror and concave mirror.
(b) concave mirror and convex mirror.
(c) plane mirror and convex mirror.
(d) convex mirror and plane mirror.
Solution 1: (c) plane mirror and convex mirror.
A picture of the same size and of the erected image is often created by the plane mirror. Convex mirrors construct erected and smaller image.
Question 2: Which of the following can be used to form a real image?
(a) Concave mirror only.
(b) Plane mirror only.
(c) Convex mirror only.
(d) Both concave and convex mirrors
Solution 2: (a) concave mirror only
Like a concave mirror, a real image may be created alone. The plane mirror and the convex mirror both form a virtual image of an object.
Question 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
(a) 2 m
(b) 1 m
(c) 0.5 m
(d) 0.25 m
Solution 3: (b) 1 m
The picture created by a plane mirror is behind the mirror at the same distance as the object is in front of it. The distance between the object and the reflection is then indicated by the distance between the object and the mirror + the distance between the mirror and the image = 0.5 m+ 0.5 m = 1 m
Question 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
(a) concave mirror or convex mirror.
(b) concave mirror or convex lens.
(c) concave mirror or concave lens.
(d) concave lens or convex lens.
Solution 4: (b) concave mirror or convex lens.
The concave mirror and convex lens form expanded images, while the convex mirror and concave lens form reduced images.
Question 5: A rainbow can be seen in the sky
(a) when the sun is in front of you.
(b) when the sun is behind you.
(c) when the sun is overhead.
(d) only at the time of sunrise.
Solution 5: (b) when the sun is behind you.
After rain and when the sunlight is low, the rainbow is formed. When your back is to the sun, a rainbow emerges.
Question 6: An erect and enlarged image can be formed by
(a) only a convex mirror.
(b) only a concave mirror.
(c) only a plane mirror.
(d) both convex and concave mirrors
Solution 6: (b) only a concave mirror.
A virtual image that is erected and expanded in size has often been created by the concave mirror while the convex mirror forms a reduced and erected image.
Question 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
(a) both the concave lens and convex lens.
(b) both concave mirror and convex mirror.
(c) both concave mirror and convex lens.
(d) both convex mirror and concave lens.
Solution 7: (c) both concave mirror and convex lens.
The concave mirror and convex lens can only form a representation of an object that is real and reversed. As a convex mirror and concave prism, an object's virtual and erect image still forms.
Question 8: An image formed by a lens is erect. Such an image could be formed by a
(a) convex lens provided the image is smaller than the object.
(b) concave lens provided the image is smaller than the object.
(c) concave lens provided the image is larger than the object.
(d) concave lens provided the image is of the same size.
Solution 8: (b) concave lens provided the image is smaller than the object.
A concave lens forms the virtual, erect and diminished representation of an object. The convex lens forms an expanded, upright, virtual picture.
Very Short Answer Questions......................
Question 9: The image formed by a lens is always virtual, erect and smaller in size for an object kept at different positions in front of it. Identify the nature of the lens.
Solution 9: The nature of the lens is Concave lens.
Question 10: Fill in the blanks:
(a) The inner surface of a steel spoon acts as a ___________ mirror.
(b) The outer surface of a flat steel plate acts as a ___________ mirror.
(c) The outer shining surface of a round bottom steel bowl acts as a __________ mirror.
(d) The inner surface of the reflector of a torch acts as a __________ mirror.
Solution 10:
(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 11: State whether the following statements are True or False.
(a) A concave lens can be used to produce an enlarged and erect image.
(b) A convex lens always produces a real image.
(c) The sides of an object and its image formed by a concave mirror are always interchanged.
(d) An object can be seen only if it emits light.
Solution 11:
- False- To create a diminished and erect image, a concave lens may be used.
- False- A virtual image is often generated by a convex lens.
- True
- False- If it reflects light falling on it, an entity can be seen.
Short Answer Questions...............
Question 12: What type of mirror is used as a side mirror in a scooter? Why is this type of mirror chosen?
Solution 12: Convex mirrors are used in a scooter as a side mirror since the image created in convex mirrors stretches over a wide area. This would allow drivers see the wide area of the traffic behind them.
Question 13: Observe the figures given in Figure 15.1 carefully.
The given figures show the path of light through lenses of two different types, represented by rectangular boxes A and B. What is the nature of lenses A and B?
Solution 13:
(A) Convex lens
(B) Concave lens
Question 14: Boojho made light from a laser torch to fall on a prism. Will he be able to observe a band of seven colours? Explain with a reason.
Solution 14: No, Boojho is unable to observe a colour band, since laser light only provides a single colour to the torch.
Question 15: State the correct sequence (1-7) of colours in the spectrum formed by the prisms A and B, shown in Figure 15.2.
Solution 15:
Question 16: The side mirror of a scooter got broken. The mechanic replaced it with a plane mirror. Mention any inconvenience that the driver of the scooter will face while using it?
Solution 16: A driver is unable to see the traffic running over the large field behind him.
Question 17: The concave reflecting surface of a torch got rusted. What effect would this have on the beam of light from the torch?
Solution 17: If a torch's concave reflective surface is rusted, a ray of light of a lower strength would be scattered.
Question 18: An erect and enlarged image of an object is formed on a screen. Explain how this could be possible.
Solution 18: On a frame, if the object is positioned upside down between F and 2F of the lens, an upright and expanded image of an object is created.
Question 19: Two different types of lenses are placed on a sheet of newspaper. How will you identify them without touching?
Solution 19: If the letters appear magnified, the lens is a convex lens and if the image appears shortened, the lens is concave.
Question 20: A shopkeeper wanted to fix a mirror which will give a maximum view of his shop. What type of mirror should he use? Give reason.
Solution 20: Shopkeeper repairs convex mirror as it shapes object representations spaced out from wide regions.
Question 21: The distance between an object and a convex lens is changing. It is noticed that the size of the image formed on a screen is decreasing. Is the object moving in a direction towards the lens or away from it?
Solution 21: The object is moving away from the lens.
Long Answer Questions....................
Question 22: Suppose we wish to obtain the real image of a distant tree. Explain two possible ways in which we can do it.
Solution 22: Two possible ways in which the real image of a distant tree can be obtained are given below:
- By using a concave mirror and a screen-
If the distance between the mirror and the object is outside the focus, a real image is created using a concave mirror.
- By using a convex lens and a screen-
In the case of convex lens, the image is very near to the lens creating a real and inverted image when the object is far away from the lens.
Question 23: It was observed that when the distance between an object and a lens decreases, the size of the image increases. What is the nature of this lens? If you keep on decreasing the distance between the object and the lens, will you still able to obtain the image on the screen? Explain.
Solution 23: The nature of the lens is convex lens.
No, the image generated is imaginary when the object is positioned next to a convex lens, which cannot be acquired on the screen.
Question 24: You are given three mirrors of different types. How will you identify each one of them?
Solution 24: We can recognize the mirrors by obtaining images of the object:
i) Plane mirror
In the case of plane mirrors, the image created will be virtual, erect and same sized as that of the object.
ii) Concave mirror
Based on the placing of the object the image created will be real or virtual, inverted or erect and expanded or diminished.
iii) Convex mirror
In case of a convex mirror, the image formation will always be virtual, erect and smaller irrespective of the fact where the object is placed.