Converging Lens and Plane Mirror Question

In summary, the problem involves a real object being placed between a convex lens and a plane mirror. Two images are observed: a real image on the left of the lens and a virtual image on the right, with a size ratio of 3:1. The location of the real object with respect to the lens can be found by using the thin lens equations and considering the distance of the real object to the mirror. The size of the real object can be compared to the virtual image using the equation for magnification. Careful consideration of signs is necessary when dealing with the magnification, especially when the virtual image is larger than the real image.
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Homework Statement


A real object is put in-between a convex lens (f = 30.0cm) and a plane mirror as shown in the figure below. Two images of the object are observed : a real image 50.0cm to the left of the lens and a virtual image to the right of the lens. The size of the virtual image is 3.00 times that of the real image.

(a) Find the location of the real object with respect to the lens. What is its size comparing with the virtual image?
(b) Find the location of the mirror with respect to the lens.

I've attached a picture of the question for easy reference.

Homework Equations

The Attempt at a Solution



I know that there are two images being formed.
The virtual image is formed in an imaging process that involves only the lens and the object. Since dobject < f = 30, the image will be virtual, upright and enlarged.
The real image is formed in an imaging process that involves both the lens and the planar mirror. The object is reflected about the plane of the planar mirror, forming a virtual object behind the surface of the mirror. This virtual image acts as the object for the converging lens and forms a real, inverted and reduced image on the left of the converging lens.

However, I'm not too sure on how to use the size of the virtual and real image to find the location of the real object.

Any help will be greatly appreciated!
 

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  • #2
Try the real object distance as 2 D + O where O is the distance of the real object from the lens
and D the distance of the real object to the mirror.
This (O) is also the object distance for the virtual image.
Together with the thin lens equations and the equation for magnification which depends only
object and image distances you should be able to solve the problem.
Be careful with signs regarding the magnification especially where the virtual image is 3X the real image
because these are two independent quantities that only depend on their associated object and image distances.
 

What is a converging lens?

A converging lens is a type of lens that is thicker in the middle and thinner at the edges. It is also known as a convex lens. This type of lens is able to bend light rays and bring them together at a focal point, creating an image.

What is a plane mirror?

A plane mirror is a flat, smooth surface that reflects light rays in a regular manner. It is also known as a flat mirror. When an object is placed in front of a plane mirror, the reflected image is the same size and shape as the object, but appears to be behind the mirror.

How are converging lenses and plane mirrors used together?

Converging lenses and plane mirrors are often used together in optical instruments, such as telescopes and microscopes. The converging lens is used to focus light rays from distant objects, and the plane mirror is used to reflect the image to the eyepiece, allowing for a magnified view.

What is the difference between a real and virtual image?

A real image is formed when light rays actually converge at a point to form an image. This image can be projected onto a screen and can be seen without the use of any additional optics. A virtual image, on the other hand, is formed when light rays appear to be coming from a point, but do not actually converge. This image cannot be projected onto a screen and is only visible when viewed through a lens or mirror.

How do you calculate the position of an image formed by a converging lens and a plane mirror?

The position of an image formed by a converging lens and a plane mirror can be calculated using the thin lens equation: 1/f = 1/di + 1/do, where f is the focal length of the lens, di is the image distance, and do is the object distance. The image will be located at a distance from the lens equal to the sum of the focal length and the image distance (di + f) when the object is placed at a distance equal to the focal length (do = f).

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