# Difference between Concave and Convex Mirror with Diagram

We see objects because light rays enter our eyes after bouncing off the objects. This bouncing of light off objects is known as reflection.

There are plane (flat) and curved mirrors. In a plane mirror the image is the same size as the object and the same way up. But it is inverted, i.e. back-to-front.

There are two types of curved mirror (convex and concave).

### What are convex mirror ?

A mirror that bulges outwards is called a convex mirror. Convex mirrors show things the right way up and usually smaller.

### What are concave mirror ?

A mirror that bulges inwards is called a concave mirror. (Remember you go into a cave!). How you appear in a concave mirror depends on how close you are to it. From close up you look bigger and right way up. Further away you look smaller and upside down.

## Difference between concave and convex mirror

The main difference between concave and convex mirrors is the most easily seen by considering how they reflect light rays parallel and close to the principal axis.

1. If the inner surface of the spherical mirror is the reflecting surface, it is called a concave mirror. If the outer surface of the spherical mirror is the reflecting surface, it is called a convex mirror.

2. A concave mirror is called a converging mirror. Convex mirror is called a diverging mirror or fisheye mirror.

3. The focus lies in front of the mirror in concave. The focus lies behind the mirror in convex.

4. A concave mirror can be projected on the screen. The convex mirror cannot be projected on the screen.

5. A concave mirror is hollowed or rounded. Convex mirror is curved or rounded like the outside of sphere or circle.

6. For concave mirror, the reflected rays converge to the focal point F located at f = +R/2 on the principal axis. Positive sign means that the rays actually converge at and subsequently emanate from the focal point. For convex mirror, f = -R/2 and is located on the principal axis behind the mirror. Negative sign means that rays “appears” to, but actually not, converge to and then emanate from the focal point.

## Image Formation by Concave Mirrors

By drawing the reflected rays by using any two of the above three ways, we can locate the image, which is either the direct intercept of the reflected rays (if the image is real) or the intercept of their extrapolations behind the mirror (if the image is virtual). An image is real if light actually converge at the image position (and so the image can be recorded by a photographic plate or visualized by a projector screen placed at the image position). Converse is true for a virtual image.

## Image formation by a concave mirror for different positions of the object

A concave mirror can reflect in two different ways:

• If the object is close, the mirror will make it appear larger and right side up.
• If the object is farther away, the mirror will make it appear smaller and upside down.

 Position of the Object Position of the Image Size of the Image Nature of the Image Image Diagram At Infinity At the focus of F High diminished, Point-sized Real and inverted Beyond C Between F and C Diminished Real and inverted At C At C Same size Real and inverted Between C and F Beyond C Enlarged Real and inverted At F At Infinity Highly enlarged Real and inverted Between P and F Behind the mirror Enlarged Virtual and erect

## Image Formation by Convex Mirrors

We can establish three similar ways to draw reflected rays for a convex mirror. It turns out the image formed by a convex mirror is always virtual, upright and diminished. So one always needs to extrapolate the reflected rays behind a convex mirror to find the image.

## Image formation by a convex mirror for different positions of the object

A convex mirror produces a small image standing right side up. It reflects back a larger area than a concave mirror does. Convex mirrors are used for security purposes in stores.

 Position of the Object Position of the Image Size of the Image Nature of the Image At Infinity At the focus of F, behind the mirror High diminished, Point-sized Virtual and erect Between infinity and the pole P of the mirror Between P and F, behind the mirror Diminished Virtual and erect

### Uses of concave mirror:

Concave mirrors are commonly used in torches, search-lights and vehicles headlights to get powerful parallel beams of light. They are often used as shaving mirrors to see a larger image of the face. The dentists use concave mirrors to see large images of the teeth of patients. Large concave mirrors are used to concentrate sunlight to produce heat in solar furnaces.

• By dentists to examine the teeth.
• Shaving mirrors.
• Astronomical telescopes.
• Solar furnaces.
• Reflector of torch.

### Uses of convex mirror:

Convex mirrors are commonly used as rear-view (wing) mirrors in vehicles. These mirrors are fitted on the sides of the vehicle, enabling the driver to see traffic behind him/her to facilitate safe driving. Convex mirrors are preferred because they always give an erect, though diminished, image. Also, they have a wider field of view as they are curved outwards. Thus, convex mirrors enable the driver to view much larger area than would be possible with a plane mirror.

• Side view mirror in vehicles.
• Vehicle mirrors.
• Magnifying glasses.
• For security purposes.
• Street light reflectors.

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Difference between Convex Mirror with Diagram vs Concave

Concave vs Convex Mirror with Diagram

Differences between Convex Mirror with Diagram vs Concave

Image Credits: Freepik

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