Convex Mirror Important Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. The images generated by _____ mirrors are incompatible with projecting on a screen since the images are inside the mirrors.

1. Concave
2. Concave
3. Plane
4. All of the above

Ans. The correct answer is b. Convex

Explanation: Because the images formed by convex mirrors are behind the mirrors, they cannot be projected on a screen.

Ques. A man stands in front of a mirror of a special shape. He finds that his image has a very small head, a fat body, and legs of normal size. What can we say about the shapes of the three parts of the mirror?

1. Concave, Convex, Plane
2. Convex, Concave, Plane
3. Convex, Plane, Concave
4. The plane, Concave, Convex

Ans. The correct answer is b. Convex, Concave, Plane

Explanation: The upper part of the mirror is a convex mirror. The central part of the mirror is concave. The lower of the mirror is a plane mirror. The image produced by a plane mirror will not vary, however, the image formed by concave and convex mirrors will.

Ques. An object stands straight in front of a mirror at a distance of 30 cm from it. He sees his erect image whose height is 1/5 of his real height. The mirror he is using is

1. Convex
2. Concave
3. Plane
4. All of the above

Ans. The correct answer is a. Convex

Explanation: Only a convex mirror can produce an upright, virtual, and diminished image of an object because the image height is 1/5 of the real height.

Ques. A convex mirror is also known as a

1. Plane mirror
2. Diverging mirror
3. Converging mirror
4. Concave mirror

Ans. The correct answer is b. Diverging mirror

Explanation: A convex mirror is also known as a diverging mirror since it diverges the ray of light incident on it.

Ques. The focal length of a convex mirror is

1. Always negative
2. Always zero
3. Always positive
4. Can be either positive or negative

Ans. The correct answer is c. Always positive

Explanation: The focal length of a convex mirror is always positive.

Ques. For a convex mirror, the center of curvature is

1. On the opposite side of the incident light
2. At the surface of the mirror
3. On the same side as the incident light
4. At the focus of the mirror

Ans. The correct answer is c. On the same side as the incident light

Explanation: For a convex mirror, the center of curvature is on the same side as the incident light.

Ques. When an object is placed in front of a convex mirror, the image formed is

1. Real, inverted, and reduced
2. Virtual, erect, and reduced
3. Real, inverted, and enlarged
4. Virtual, erect, and enlarged

Ans. The correct answer is b. Virtual, erect, and reduced

Explanation: When an object is placed in front of a convex mirror, the image formed is virtual, erect, and reduced.

Ques. A convex mirror forms a virtual image when the object is placed

1. At its focal point
2. In front of its focal length
3. Beyond its focal length
4. Between its focal length and the mirror

Ans. The correct answer is b. In front of its focal length

Explanation: A convex mirror forms a virtual image when the object is placed in front of its focal length.

Ques. The power of a convex mirror is measured in

1. Watts (W)
2. Ohms (Ω)
3. Newtons (N)
4. Diopters (D)

Ans. The correct answer is d. Diopters (D)

Explanation: The power of a convex mirror is measured in Diopters (D). It is given by the reciprocal of the focal length of the mirror.

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Short Answers Questions [2 Marks Questions]

Ques. What is a convex mirror?

Ans. Convex mirrors, also known as diverging mirrors, have a reflecting surface that bulges out towards the light source. The convex mirror always provides virtual and erect images regardless of the position of the object.

Ques. What is an image?

Ans. An image is defined as a collection of light ray focus points emitted by an object. A real image is a collection of converging/diverging ray focus points, whereas a virtual image is a collection of diverging or converging ray extensions.

Ques. Why is a convex mirror called a diverging mirror?

Ans. A convex mirror is also known as a diverging mirror. It is due to the behavior of the mirror that light beams diverge upon reflection. When a light ray is directed at this mirror, the initially parallel light rays that constitute the beam deviate/diverge after reaching the reflecting surface of the convex mirror.

Ques. What is a convex lens?

Ans. A convex lens is one with two convex surfaces that allow light beams to converge. The convex lens is narrow along the edges and thick in the center. This lens is capable of producing both real and virtual images.

Ques. What is the focal length?

Ans. The focal length of an optical system is the inverse of its optical power; it measures how strongly the system converges or diverges light. A positive focal length system converges light, whereas a negative focal length system diverges light.

Ques. What is a mirror?

Ans. The mirror is a device that causes light to reflect from its surface with almost no diffusion.

Ques. What is the relation between the focal length and radius of curvature of a convex mirror?

Ans. The relation between the focal length and radius of curvature of a convex mirror is given by

f = R/2

Where

• R is the radius of curvature
• f is the focal length of a convex mirror

Ques. Define mirror formula.

Ans. The Mirror formula shows the relation between the object distance (u), image distance (v), and focal length (f) of a Spherical Mirror.

Ques. What is the mirror formula for a convex mirror?

Ans. The mirror formula for a convex mirror is given by

1/f = 1/u + 1/v

Where

• f is the focal length
• u is the distance of the object
• v is the distance of the image

Ques. Define the magnification of a convex mirror.

Ans. Magnification is the ratio of the height of the image to the height of the object. It is given by

M = (Height of the image)/(Height of the object) = h’/h

For a convex mirror, the magnification is always less than one.

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Long Answers Questions [3 Marks Questions]

Ques. Explain the characteristics of images generated by convex mirrors.

Ans. Convex mirror images are always virtual, diminished, and upright. 

• In reality, a beam of light did not penetrate the image in this case; its extension did, just like in a normal mirror. 
• The images get larger as the objects move closer to the mirror until they are about the size of the objects when they contact the mirror. 
• As the objects move away, images become smaller and closer to the focus until they are reduced to a point (visible) when the object is at an infinite distance.

Ques. What are the fundamental concepts of a convex mirror?

Ans. A convex mirror is one with a reflecting surface that faces the source of light. 

• Because these mirrors bounce light outwards, they are not used to focus light. 
• Convex mirrors form a virtual image, and the center of curvature is an imaginary point within the mirror. 
• It is not physically accessible (virtual image). As a result, because the images formed by these particular mirrors are inside the mirrors, they are unsuitable for projection on a screen. 
• The images are smaller than the object, but they get larger as they approach the mirror. 
• Because the normal to the surface differs at each place, a parallel beam of light diverges after reflection by the surface of a convex mirror.

Ques. What are the most familiar uses of convex mirrors?

Ans. The most familiar uses of convex mirrors are

• A convex mirror is typically used in hallways of schools, flats, hotels, and hospitals to offer an expanded view of the whole room. 
• These spherical mirrors are also used in highways, streets, and driveways to offer vehicles a broader view at turns, curves, and other crossings where visibility is poor.
• Convex mirrors serve as an essential security element in most automated teller machines (ATMs) to allow consumers to see what is going on behind them.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the applications of convex mirrors?

Ans. The following are the applications of convex mirrors

• Automobiles: By providing drivers with an extensive overview of the back and side views of the roadways and surroundings, they can avoid risky situations and prevent accidents. The convex mirror is one of the most important parts that provides a sharper rear vision of the road to ensure optimal safety at all times.
• Automated Teller Machines: Convex mirrors are placed near ATMs or automated teller machines to allow consumers to determine whether someone is standing behind them. This is used to safeguard the safety of customers while using an ATM.
• In Cameras: Some smartphones include a selfie camera that allows users to take a self-portrait photograph.
• In Sunglasses: Convex mirrors are used in the production of a sunglass lens. The main objective is to reflect sunlight away from the person wearing the glasses.
• In the Magnifying Glass: When two convex mirrors are put close to each other, they can be combined to produce a magnifying glass.

Ques. What are the differences between a concave mirror and a convex mirror?

Ans. The following are the differences between a concave mirror and a convex mirror

Ques. Find the position of the object which when placed in front of a convex mirror of focal length 20 cm produces a virtual image, which is half the size of the object.

Ans. Given

• The focal length of the convex mirror, f = 20 cm
• h’ = - h/2 (h’ is the image height and h is the object height)

According to the formula of magnification, we have

m = h’/h = v/u

On substituting the values, we get

(-h/2)/h = v/u

⇒ v = (-1/2)u

According to the mirror formula, we have

1/f = 1/v + 1/u

On substituting the value v = (-1/2)u in above equation, we get

1/f = 1/(-1/2)u + 1/u

⇒ 1/f = - (2/u) + 1/u

On substituting f = 20 cm, we get

u = - 20 cm

Hence, the object is at 20 cm in front of the mirror.

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