For what position of the object does a concave mirror form a virtual and erect image explain with the help of Ray diagram?

The surface that reflects nearly every type of light that is incident on it is known as a mirror. A mirror can have a flat surface or a curved surface. A mirror with a flat surface is called a plane mirror, and a mirror with a curved surface is called a spherical mirror. In this article, let us learn about convex mirrors and concave mirrors.

A mirror is a reflective surface that bounces off light, producing either a real image or a virtual image. When an object is placed in front of a mirror, the image of the same object is seen in the mirror. The object is the source of the incident rays and the image is formed by the reflected rays. Based on the intersection of light rays, the images are classified as either a real images or a virtual images. A real image occurs when the light rays actually intersect while virtual images occur due to the apparent divergence of light rays from a point.

Ray diagrams help us trace the path of the light for the person to view a point on the image of an object. The Ray diagram uses lines with arrows to represent the incident and reflected ray. It also helps us trace the direction in which the light travels.

Mirrors are made into different shapes for different purposes.

The two of the most prominent types of mirrors are:

• Plane Mirrors
• Spherical Mirrors

A plane mirror is a flat, smooth reflective surface. A plane mirror always forms a virtual image that is upright, and of the same shape and size as the object, it is reflecting. A spherical mirror is a mirror that has a consistent curve and a constant radius of curvature. The images formed by a spherical mirror can either be real or virtual. Spherical mirrors are of two types as:

• • Concave Mirror
  • Convex Mirror

In the next few sections, let us learn in-depth about the characteristics of convex and concave mirrors and the images formed by them when the object is kept at different positions.

Spherical mirrors are mirrors having curved surfaces that are painted on one of the sides. Spherical mirrors in which inward surfaces are painted are known as convex mirrors, while the spherical mirrors in which outward surfaces are painted are considered concave mirrors.

If a hollow sphere is cut into parts and the outer surface of the cut part is painted, then it becomes a mirror with its inner surface as the reflecting surface. This type of mirror is known as a concave mirror.

• Light converges at a point when it strikes and reflects back from the reflecting surface of the concave mirror. Hence, it is also known as a converging mirror.
• When the concave mirror is placed very close to the object, a magnified, erect and virtual image is obtained.
• However, if we increase the distance between the object and the mirror then the size of the image reduces and a real and inverted image is formed.
• The image formed by the concave mirror can be small or large and can be real or virtual.

If the cut part of the hollow sphere is painted from the inside, then its outer surface becomes the reflecting surface. This kind of mirror is known as a convex mirror.

• A convex mirror is also known as a diverging mirror as this mirror diverges light rays when they strike its reflecting surface.
• Virtual, erect, and diminished images are always formed with convex mirrors, irrespective of the distance between the object and the mirror.

Guidelines for Rays Falling on the Concave and Convex Mirrors

1. When a ray strikes concave or convex mirrors obliquely at its pole, it is reflected obliquely making the same angle with the principal axis.
2. When a ray, parallel to the principal axis strikes concave or convex mirrors, the reflected ray passes through the focus on the principal axis.
3. When a ray, passing through focus strikes concave or convex mirrors, the reflected ray will be parallel to the principal axis.
4. A ray passing through the centre of curvature of the spherical mirror will retrace its path after reflection.

See the video below to learn about the reflection from spherical mirror.

By changing the position of the object from the concave mirror, different types of images can be formed. Different types of images are formed when the object is placed:

1. At the infinity
2. Beyond the centre of curvature
3. At the centre of curvature
4. Between the centre of curvature and principal focus
5. At the principal focus
6. Between the principal focus and pole

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Recommended Video

• Concave Mirror Ray Diagram lets us understand that, when an object is placed at infinity, a real and inverted image is formed at the focus. The size of the image is much smaller compared to that of the object.

• When an object is placed behind the center of curvature, a real image is formed between the center of curvature and focus. The size of the image is smaller than compared to that of the object.

• When an object is placed at the center of curvature and focus, the real image is formed at the center of curvature. The size of the image is the same as compared to that of the object.

• When an object is placed in between the center of curvature and focus, the real image is formed behind the center of curvature. The size of the image is larger than compared to that of the object.

• When an object is placed at the focus, the real image is formed at infinity. The size of the image is much larger than compared to that of the object.

• When an object is placed in between focus and pole, a virtual and erect image is formed. The size of the image is larger than compared to that of the object.