Mirrors are the surfaces that reflect almost all types of incident light rays that hit their surface. The mirror can have either a plane or a curved surface. On this basis, mirrors are divided into two: Spherical Mirrors and Plane Mirrors. The plane mirrors simply mirror having plain and polished reflecting surfaces while Spherical mirrors have curved reflecting surfaces. Based on the curved reflecting surface spherical mirrors are further divided into two: Concave and Convex Mirrors. In concave mirrors, the reflection takes place from the inner surface of the spherical mirror. The image formed by the concave mirrors is real and inverted. However, in the case of convex mirrors, the reflection takes place from the outer surface of the spherical mirror. The image formed by the convex mirrors is virtual and erect. Show
What are Mirrors?
When an object is placed in front of a mirror, the mirror reflects the image of the same object. The incident rays are coming from the object, and the reflected rays are what produce the image. The classification of the images as real or virtual depends on where the light rays intersect. The two types of mirrors that are most commonly used are:
The most typical mirrors are flat and are referred to as “plane mirrors.” A fine layer of silver nitrate or aluminum is deposited behind a flat piece of glass to construct plane mirrors. When a light beam strikes a plane mirror, the light ray is reflected in such a way that it makes an equal angle with the incident ray that is, the angle of reflection is equal to the angle of incidence. Spherical Mirrors
The reflecting surface of such mirrors is considered to form a part of the surface of any sphere. Those mirrors which possess reflecting surfaces which are spherical are called spherical mirrors. Important Terms used in Spherical Mirrors
Types of Spherical MirrorsSpherical Mirrors are categorized into two types:
Concave Mirror
A concave mirror or converging mirror is a type of mirror that is bent towards the inwards side in the middle. Moreover, by looking in this mirror, we will feel that we are looking in a cave. We tend to use the mirror equation to deal with a concave mirror. The equation for these mirrors determines the position of the object and the accurate size of the object. The angle of incidence in the concave mirror is not the same as the angle of reflection. Moreover, the angle of reflection, in this case, depends on the area on which the light hits. Properties of Concave Mirrors
Applications of Concave Mirrors
Image Formation by Concave Mirror and their ray diagramsWhen the object is placed at infinity As the parallel rays from the object converge at the principal focus, F of a concave mirror; after reflection through it. Therefore, when the object is at infinity the image will form at F.
When the object is placed between infinity and the Centre of Curvature When the object is placed between infinity and the center of curvature of a concave mirror then the image is formed between the center of curvature (C) and focus (F).
Object at Centre of Curvature (C) Whenever we place our object at the center of curvature (C) of a concave mirror, we get a real and inverted image formed at the same position.
The object is kept between the Centre of curvature (C) and Principal Focus (F) When we keep the object somewhere between the center of curvature and the principal focus of the concave mirror, a real image is formed placed beyond the center of curvature (C). Object at Principal Focus (F) When the object is placed at the principal focus (F) of a concave mirror, a highly enlarged image of the object is formed at infinity.
The object between Principal Focus (F) and Pole (P) When the object is placed anywhere between the principal focus and the pole of a concave mirror, we get an enlarged, virtual and erect image formed behind the mirror.
Convex Mirror
The back of the mirror is shaded so that reflection only takes place from the outward bulged part. The surface of the spoon which bulged outwards can be assumed to be a convex mirror. It is also known as a diverging mirror as the light after reflecting through its surface diverges in many directions but appears to meet at some points where the virtual, erect image of diminished size is formed. Properties of Convex Mirror
Application of Convex Mirror
Image Formation by Convex Mirror and their ray diagramsTwo possibilities of the position of the object are possible in the case of a convex mirror, which is when the object is at infinity and the object is between infinity and the pole of a convex mirror. Object at infinity Whenever the object is kept at infinity, we observe that a point-sized image is formed at the principal focus behind the convex mirror.
Object is kept between infinity and the pole Whenever the object is kept anywhere between the infinity and the pole of a convex mirror, then we get a diminished, virtual and erect image formed between the pole and focus behind the mirror.
Mirror FormulaTo do the sums related to the spherical mirrors, the formula used is known as the mirror formula. It is used to calculate the focal length, image distance, object distance, and also magnification or any other thing required. We usually put the formula first and then put the signs so as to do the sums to minimize any error which can be generated. The sign conventions which are to be followed while using the mirror formula are fixed so from the above-given diagram we can easily put the signs according to the requirement to get the required result.
Sign Conventions for Spherical Mirrors
Solved Examples on Concave and Convex MirrorsExample 1: What is the image distance in the case of a concave mirror if the object distance is 4 cm? It is given that the focal length of the mirror is 2 cm. Solution:
Example 2: What is the image distance in the case of a concave mirror if the object distance is 32 cm? It is given that the focal length of the mirror is 16 cm. State the nature and the size of the image which is formed. Solution:
Example 3: What is the image distance in the case of the convex mirror if the object distance is 12 cm? It is given that the focal length of the mirror is 12 cm. Solution:
Example 4: What is the image distance in the case of a concave mirror if the object distance is 10 cm? It is given that the focal length of the mirror is 10 cm. Solution:
Example 5: What is the image distance in the case of a convex mirror if the object is at the focus of the mirror? It is given that the focal length of the mirror is 10 cm. What can u say about the nature of the image formed and also the size? Solution:
FAQs on Concave and Convex MirrorsQuestion 1: Which mirror is used by the dentist? Answer:
Question 2: What is another name for the concave mirror? Answer:
Question 3: What are the applications of convex mirrors? State any two. Solution:
Question 4: What is the difference between a concave mirror and a convex mirror? Answer:
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