Question

the size of the image due to a convex mirror will increase when the object is

a)moving away from the mirror.
b)moving towards the mirror.
c)`moving between center of curvature and principal focus.
d)moving between pole and focus.

Answer 1

Let us know about convex mirrors and concave mirrors. Mirror is a surface which reflects a clear image. Images can be of two types: Real image and Virtual image. An image which can be formed on the screen is known as real image and the one which cannot be formed on screen is known as virtual image. These images are formed when light falls on a mirror from the object and is reflected back by the mirror on the screen. There can be two types of mirror: Curved mirror and plane mirror. If curved mirror is a part of sphere then it is known as spherical mirror. The image formed by a plane mirror is always a virtual image as it cannot be obtained on a screen. Image formed by spherical mirror can be either real or virtual. Spherical mirrors are of two types:

Convex mirrorsConcave mirrors



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

Convex mirror: If the other cut part of the hollow sphere is painted from inside, then its outer surface becomes the reflecting surface. This kind of mirror is known as convex mirror. Convex mirror is also known as diverging mirror as this mirror diverges light when they strike on its reflecting surface. Virtual, erect and diminished images are always formed with convex mirrors, irrespective of the distance between the object and the mirror. Apart from other applications, convex mirror is mostly used as rear view mirror in vehicles.

Spherical mirrors are the mirrors having curved surfaces which 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 known as concave mirrors. Concave mirrors are also known as a converging mirror since the rays converge after falling on the concave mirror while the convex mirrors are known as diverging mirrors as the rays diverge after falling on the convex mirror. In this article, we will learn about image formation by concave and convex mirrors.

Guidelines for Rays Falling on the Concave and Convex Mirrors

When a ray strikes concave or convex mirrors obliquely at its pole, it is reflected obliquely.When a ray, parallel to principle axis strikes concave or convex mirrors, the reflected ray passes through the focus on the principle axis.When a ray, passing through focus strikes concave or convex mirrors, the reflected ray will pass parallel to the principle axis.A ray passing through the center of curvature of the spherical mirror will retrace its path after reflection.

Image formation by Concave and Convex Mirrors:

Ray Diagram for Concave Mirrors:

When an object the is placed at infinity, a real image is formed at the focus. The size of the image is much smaller as 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 as 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 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 smaller as 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 as compared to that of the object.



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



Ray Diagram for Convex Mirrors:

When an object is placed at infinity, a virtual image is formed at the focus. The size of the image is much smaller as compared to that of the object.



When an object is placed at a finite distance from the mirror, a virtual image is formed between pole and focus of the convex mirror. The size of the image is smaller as compared to that of the object.