A mirror is a surface that reflects almost all incident light. Mirrors come in two types: those with a flat surface, known as plane mirrors, and those with a curved surface, called spherical mirrors. In this article, we will explore two specific types of spherical mirrors: convex mirrors and concave mirrors. We will also delve into the concept of ray diagrams, which help us understand how light behaves when it interacts with these mirrors. By examining the ray diagram of a spherical mirror, we can gain insights into the fascinating phenomena of reflection and image formation.
A mirror plays a fascinating role in reflecting light, resulting in the formation of images. When an object is placed in front of a mirror, we observe its reflection. Incident rays originate from the object, and the reflected rays converge or appear to diverge to create the image. Images formed by mirrors can be classified as real image or virtual image. Real images are produced when light rays converge and intersect, while virtual images are formed when light rays appear to diverge from a point.
Ray diagrams are employed to comprehend the behaviour of light and better understand image formation. These diagrams use lines with arrows to represent incident and reflected rays, allowing us to trace their paths and interactions with the mirror. By interpreting ray diagrams, we gain valuable insights into how images are formed and a deeper understanding of how our eyes perceive objects through reflection.
A plane mirror is a flat, smooth reflective surface with a clear, undistorted reflection. When an object is reflected in a plane mirror, it always forms a virtual image that is upright, of the same shape and size as the object.
On the other hand, a spherical mirror exhibits a consistent curvature. It possesses a constant radius of curvature (In the context of spherical mirrors, the radius of curvature refers to the distance between the centre of the spherical mirror and its curved surface.). Spherical mirrors can create both real and virtual images, depending on the position of the object and the mirror. Spherical mirrors are further categorized into concave and convex mirrors, each with distinct properties and image formation characteristics.
In the upcoming sections, we will detail the characteristics of convex and concave mirrors, along with a comprehensive understanding of the images formed by these mirrors when the object is placed at various positions with the help of ray diagrams.
A concave mirror is a curved mirror where the reflecting surface is on the inner side of the curved shape. It has a surface that curves inward, resembling the shape of the inner surface of a hollow sphere. Concave mirrors are also converging mirrors because they cause light rays to converge or come together after reflection. Depending on the position of the object and the mirror, concave mirrors can form both real and virtual images.
A convex mirror is a curved mirror with the reflecting surface on the curved shape’s outer side. It has a surface that curves outward, resembling the shape of the outer surface of a sphere. Convex mirrors are also known as diverging mirrors because they cause light rays to diverge or spread out after reflection. Convex mirrors always form virtual, erect, and diminished images, regardless of the object’s position. They are commonly used in applications requiring a wide field of view, such as rear-view mirrors and security mirrors.
By understanding some crucial guidelines for ray incidence on concave and convex mirrors, we can predict and analyze the behaviour of light rays, aiding in constructing accurate ray diagrams and comprehending image formation processes.
Oblique Incidence: When a ray strikes a concave or convex mirror at its pole, it is reflected obliquely, making the same angle as the principal axis. This principle of reflection ensures that the angle of incidence is equal to the angle of reflection, maintaining the symmetry of the reflected rays.
Parallel Incidence: When a ray parallel to the principal axis strikes a concave or convex mirror, the reflected ray follows a specific path. In the case of a concave mirror, the reflected ray passes through the focus on the principal axis. Similarly, for a convex mirror, the reflected ray originates from the focus on the same side as the incident ray.
Focus Incidence: When a ray passes through the focus and strikes a concave or convex mirror, the reflected ray will be parallel to the principal axis. This characteristic holds for concave and convex mirrors and is crucial in determining the path of reflected rays.
Centre of Curvature Incidence: A ray passing through the centre of curvature of a spherical mirror will retrace its path after reflection. This principle illustrates that when a ray hits the mirror’s centre of curvature, it undergoes reflection and follows the exact same path in the opposite direction.
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The object’s position in relation to a concave mirror affects the type and characteristics of the image formed. Different scenarios result in different types of images:
A real and inverted image is formed at the focus when the object is placed at infinity. The size of the image is significantly smaller than that of the object.
When the object is positioned beyond the centre of curvature, a real image is formed between the centre of curvature and the focus. The size of the image is smaller compared to that of the object.
When the object is placed at the centre of curvature, or the focus, a real image is formed at the centre of curvature. The size of the image remains the same as that of the object.
If the object is located between the centre of curvature and the focus, a real image is formed behind the centre of curvature. The size of the image is larger compared to that of the object.
When the object is positioned exactly at the focus, a real image is formed at infinity. The size of the image is much larger than that of the object.
Placing the object between the focus and the pole results in the formation of a virtual and erect image. The size of the image is larger compared to that of the object.
S. No
Position of Object
Position of Image
Size of Image
Nature of Image
1
Object at Infinity
At the Focus
Highly Diminished
Real and Inverted
2
Object Beyond the Centre of Curvature
Between the Centre of Curvature and Focus
Diminished
Real and Inverted
3
Object at the Centre of Curvature or Focus
At the Centre of Curvature
Same Size
Real and Inverted
4
Object Between the Centre of Curvature and Focus
Behind the Centre of Curvature
Enlarged
Real and Inverted
5
Object at the Focus
At Infinity
Highly Enlarged
Real and Inverted
6
Object Between the Focus and the Pole
Behind the Mirror
Enlarged
Virtual and Erect
Related Articles
A convex mirror produces specific characteristics in the images formed. Let’s explore the types of images formed by a convex mirror.
When the object is positioned at infinity, a virtual image is formed at the focus of the convex mirror. The size of the image is significantly smaller than that of the object.
When an object is placed at a finite distance from the mirror, a virtual image is formed between the pole and the focus of the convex mirror. The size of the image is smaller than compared to that of the object.
It’s important to note that in both cases, the images formed by a convex mirror are always virtual and erect. The nature of a convex mirror causes light rays to diverge upon reflection, creating virtual images with reduced sizes. Understanding these principles helps us accurately predict the characteristics of images formed by convex mirrors.
Enhance your learning experience and deepen your understanding of convex and concave mirrors by watching our carefully curated collection of videos. These videos provide valuable insights into the properties, image formation, and practical applications of spherical mirrors. These videos are designed to make your learning journey more enjoyable and informative.
Frequently Asked Questions – FAQs
Q1
Convex mirrors are diverging mirrors that bulge outward. They reflect light away from the mirror, causing the image formed to be smaller than the object. As the object gets closer to the mirror, the image appears larger.
Q2
Concave mirrors have a curved inward reflective surface. They reflect light inward towards a focal point. The image formed by a concave mirror varies based on the distance between the object and the mirror.
Q3
Examples of concave mirrors include torch lights and automobile headlights. Convex mirrors can be seen in magnifying glasses and telescopes.
Q4
Concave mirrors have a reflective inner surface, while convex mirrors have a reflective outer surface.
Q5
Yes, you can. When an object is placed in front of a concave mirror, a magnified image is formed when the object is close to the mirror, and an inverted image is formed when the object is farther away. On the other hand, a convex mirror always forms a small and upright image of the object.
Q6
Yes, concave mirrors can form virtual images when the object is within the focal point. These images are always upright and magnified.
Q7
The main advantage of convex mirrors is their wide angle of view, allowing for a larger area to be observed or monitored.
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Concave mirrors magnify objects in focus. They're used for shaving or applying makeup because they reflect 'real,' almost 3-dimensional images. Concave mirrors are curved, and as light hits the upper and lower portions of the mirror, the image is focused at a central point, projected outward from the mirror itself. This means you do not have to look into the mirror itself to see your reflection, and the image is clearer and sharper than with a flat mirror.