Image Formation by a Curved Mirror
Image formation by a curved mirror depends on the type of mirror and the position of the object.
A concave mirror can form different types of images. A convex mirror always forms a virtual, erect and diminished image.
Rules for Image Formation by a Spherical Mirror
⭐ A ray parallel to the principal axis passes through the focus after reflection in a concave mirror.
⭐ A ray passing through the focus becomes parallel to the principal axis after reflection.
⭐ A ray passing through the centre of curvature returns along the same path after reflection.
⭐ A ray incident at the pole reflects according to the laws of reflection.
Image Formation by a Concave Mirror
Object at Infinity
Image is formed at the focus.
Nature: real and inverted.
Size: highly diminished, almost point sized.
Object Beyond C
Image is formed between F and C.
Nature: real and inverted.
Size: diminished.
Object at C
Image is formed at C.
Nature: real and inverted.
Size: same as the object.
Object Between C and F
Image is formed beyond C.
Nature: real and inverted.
Size: enlarged.
Object at F
Image is formed at infinity.
Nature: real and inverted.
Size: highly enlarged.
Object Between F and P
Image is formed behind the mirror.
Nature: virtual and erect.
Size: enlarged.
💡 Drag the object to the left or right and observe how the image changes.
| Object Position | Image Position | Nature and Size |
|---|---|---|
| At infinity | At F | Real, inverted, highly diminished |
| Beyond C | Between F and C | Real, inverted, diminished |
| At C | At C | Real, inverted, same size |
| Between C and F | Beyond C | Real, inverted, enlarged |
| At F | At infinity | Real, inverted, highly enlarged |
| Between F and P | Behind the mirror | Virtual, erect, enlarged |
Image Formation by a Convex Mirror
A convex mirror always forms an image behind the mirror. The image is virtual, erect and diminished.
Image by Convex Mirror
The image is always formed behind the mirror, between the pole and the focus.
It is virtual, erect and smaller than the object.
Easy Memory Trick
⭐ For a concave mirror, the image changes with object position.
⭐ If the object is outside F, the image is real and inverted.
⭐ If the object is between F and P, the image is virtual, erect and enlarged.
⭐ For a convex mirror, the image is always virtual, erect and diminished.
Common Mistakes
| Mistake | Correct Idea |
|---|---|
| A concave mirror always forms a real image. | When the object is between F and P, a concave mirror forms a virtual image. |
| A convex mirror can form an enlarged real image. | A convex mirror always forms a virtual, erect and diminished image. |
| Image at infinity means no image is formed. | It means the reflected rays are parallel and meet very far away. |
Questions and Answers
It is the formation of an image by reflected rays from a curved mirror.
It depends on the position of the object in front of the mirror.
The image is formed at the focus. It is real, inverted and highly diminished.
The image is formed at C. It is real, inverted and of the same size as the object.
The image is formed behind the mirror. It is virtual, erect and enlarged.
A convex mirror always forms a virtual, erect and diminished image.
An image formed by the actual meeting of rays is called a real image. It can be obtained on a screen.
An image formed by the apparent meeting of rays is called a virtual image. It cannot be obtained on a screen.