How do I know if the image is real or virtual?

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Homework Help Overview

The discussion revolves around determining whether an image formed by a lens is real or virtual, particularly in the context of a converging lens and magnification. The original poster presents a scenario involving object distance and magnification equations but seeks clarification on the nature of the image.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between object distance, focal length, and image characteristics. Questions are raised about how to draw diagrams without knowing the object's position relative to the focal length and the implications of image size on its nature.

Discussion Status

The discussion is active, with participants providing insights into the conditions under which images are real or virtual. Some guidance has been offered regarding the use of diagrams and the specific case of magnifying glasses, though multiple interpretations are still being explored.

Contextual Notes

There is a noted uncertainty about the object's position relative to the focal length, which affects the understanding of image formation. Participants reference external diagrams and examples that may not align with their assumptions.

izMuted
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Homework Statement


ae476d4f6593d54e328badcc49f9ecd0.png

I know that the object distance is 15 using the equation m = - (v/u)
(+ or - depending on real / virtual) 2 = (+ or -) 30/u
u = 15

However how do I know if the image is real or virtual?

Homework Equations


m = - (v/u)

The Attempt at a Solution

 
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Have you tried drawing the diagram, something like this:
u14l5c1.gif


Where would the image have to be to be bigger than the object?

Which side is known as the real side, which side is known as the virtual side and why?
 
How do I draw the diagram when I don't know if the object is within / outside the focal length?
Also I used to think that because the image is bigger it must be virtual, however there are some diagrams on the internet where the image is bigger and the object is outside the focal length, like here:
u14l5da6.gif
 
"the lens is used as a magnifying glass"- usually when using a magnifying glass is the image virtual or real?
 
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As far as I know, in a converging lens, only when the object is between the optical centre and the focal length that the image is virtual (i.e. the setting used in a magnifying glass).
 
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Ah yeah the magnifying glass part makes sense - thanks for explaining
 
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