Image Formation and Uses of Spherical Mirrors

we must have seen rear-view mirrors of vehicles.

We see the difference between actual size and image of object due to spherical mirrors.

Spherical Mirrors are used by us for a variety of purposes .

We use Concave Mirrors to obtain magnified images; which helps us in shaving

Concave Mirrors are also used as head-mirrors by doctors to examine the eye, ear or throat.

Convex Mirrors are used in blind turns to provide a wide range of view.

We use spherical mirrors of Concave or Convex type, depending on the requirement of the image.

Before understanding image formation, let us acquaint ourselves to some terms.

A ray that originates from the object and strikes the surface of the mirror is known as the Incident Ray.

The incident ray after reflecting off the surface of the mirror; becomes the reflected ray.

The angle between the Incident Ray and the normal at the point of incidence is called the angle of incidence ().

The angle between the Reflected Ray and the normal at the point of incidence is called the angle of reflection ().

According to laws of reflection, .

The distance between the pole and the center of curvature of the mirror is called the Radius of Curvature ().

Center of Curvature, of spherical mirrors is the centre of the hollow sphere of which the mirror is a part of .

Pole is the midpoint of the reflecting surface of the mirror .

Principle Axis is an imaginary line passing through the pole and the centre of curvature of the Spherical Mirror.

Focus, is a point, where light rays travel parallel to the principal axis, will converge to or appear to diverge from, after reflecting. from the mirror.

Now, let us see different cases of image formation .

Let us see the case when the incident ray is parallel to the principal axis.

In case of a concave mirror, when incident ray is parallel to the principal axis, the ray is converged at a point after they strike and gets reflected back from the reflecting surface.

In case of a convex mirror, when incident ray is parallel to the principal axis, the ray after reflection appears to diverge from its focus.

Not let us see the case in which the incident ray passes through the focus.

In case of a concave mirror, incident ray after passing through the focus becomes parallel to the principal axis .

In case of a convex mirror, incident ray which appears to pass through the focus becomes parallel to the principal axis after reflecting off the mirror .

Lets see the case when the incident ray passes through the Centre of Curvature .

In the case of concave mirror, when incident light passes through the centre of curvature of the mirror it retraces it's path back after reflection.

Likewise is the case in a convex mirror as well it retraces its path but appears to be coming from the centre of curvature.

Now, let's discuss the Image Formation in case of Concave Mirrors .

When the object is at infinity, the rays reflects back from the mirror and intersect at the focus of the mirror.

The image formed is real, inverted, highly diminished and forms at .

When object is placed beyond centre of curvature, the rays reflect back and and intersect somewhere between and .

The image formed in this case is real, inverted, diminished and between and .

When object is at centre of curvature (), the image formed is also at and is real, inverted and of same size.

When the object is between and , the image is formed beyond and is real, inverted and larger than object.

When the object is at , the image is real, inverted, magnified and at infinity.

When the object is between and the pole , the image is formed behind the mirror and is virtual, erect and magnified.

Now, let's discuss the Image Formation in case of Convex Mirrors .

When the object is at infinity, the rays after reflecting off the Convex Mirror appear to diverge from its focus.

The image is formed at and is virtual, erect and highly diminished in size.

When object is between infinity and pole- a diminished, virtual and erect image is formed between pole and focus behind the mirror.

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