# Image from object at a focal point of mirror

• Alexander83
In summary, the conversation discusses the behavior of images formed by a converging mirror or lens when an object is placed at different distances. The image is inverted and grows in size as the object moves closer, but when it reaches the focal point, it becomes large and blurry before flipping upright and shrinking. The question raised is why this happens, as the rays from the object at the focal point should theoretically reflect as parallel and be able to form an image. The confusion is further compounded by the fact that our eyes can focus on extremely distant objects, but not on the reflected light from an object at the focal point. The explanation given is that the eye has its own set of optical elements that affect the formation of images.
Alexander83
Hi all,
If I place an object far away from a converging mirror or lens and start to move it closer, I note that I get an inverted, real image that steadily grows in size. As the object crosses the focal point the image becomes incredibly large and blurry and then flips upright and begins to shrink in size.

My question concerns what's going on with the image of the object right when the object is at the mirror's focal point. I understand, based on tracing rays, that diverging rays eminating from a point on the object in this location will interact with the mirror so that they reflect as parallel rays and thus will never converge to an image point either in front nor behind the mirror.

My confusion is that I am able to focus on extremely distant objects like stars (often said to be "at infinity")and form an image in the back of my retina of these objects. These objects are so distant that their rays are effectively parallel.

So what is different about the reflected light from an object placed at the focal point of a mirror that prevents my eye from being able to focus this light to form an image on my retina? I sense I'm missing something fundamental here.

Thanks!

Chris.

Last edited:
You will easily be able to focus on an object placed at the focal point of a mirror/lens. Remember that your eye adds another set of optical elements to the mix so it's not simply a single lens/mirror situation anymore.

## 1. What is the focal point of a mirror?

The focal point of a mirror is the point where parallel rays of light converge after reflecting off the surface of the mirror.

## 2. How is an image formed from an object at the focal point of a mirror?

When an object is placed at the focal point of a mirror, the reflected rays of light will appear to be coming from the same point, resulting in a virtual image that is upright and the same size as the object.

## 3. Can an image be formed if the object is placed beyond the focal point of a mirror?

Yes, an image can still be formed when the object is placed beyond the focal point of a mirror. However, the image will be inverted and larger than the object.

## 4. What type of image is formed from an object at the focal point of a concave mirror?

When an object is placed at the focal point of a concave mirror, a virtual image is formed that is upright and the same size as the object.

## 5. How does the distance of the object from the focal point affect the size of the image formed?

The distance of the object from the focal point of a mirror has a direct impact on the size of the image formed. If the object is placed closer to the focal point, the image will be larger. If the object is placed further away, the image will be smaller.

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