What is Virtual image: Definition and 29 Discussions

In optics, a virtual image is defined as the collection of focus points of light rays coming from an object. A real image is the collection of focus points made by converging rays, while a virtual image is the collection of focus points made by extensions of diverging rays. In other words, a virtual image is found by tracing real rays that emerge from an optical device (lens, mirror, or some combination) backward to perceived or apparent origins of ray divergences. In diagrams of optical systems, virtual rays are conventionally represented by dotted lines.
Because the rays never really converge, a virtual image cannot be projected onto a screen. In contrast, a real image can be projected on the screen as it is formed by rays that converge on a real location. A real image can be projected onto a diffusely reflecting screen so people can see the image (the image on the screen plays as an object to be imaged by human eyes)
A plane mirror forms a virtual image positioned behind the mirror. Although the rays of light seem to come from behind the mirror, light from the source only exists in front of the mirror. The image in a plane mirror is not magnified (that is, the image is the same size as the object) and appears to be as far behind the mirror as the object is in front of the mirror.
A diverging lens (one that is thicker at the edges than the middle) or a convex mirror forms a virtual image. Such an image is reduced in size when compared to the original object. A converging lens (one that is thicker in the middle than at the edges) or a concave mirror is also capable of producing a virtual image if the object is within the focal length. Such an image will be magnified. In contrast, an object placed in front of a converging lens or concave mirror at a position beyond the focal length produces a real image. Such an image may be magnified or reduced depending on the position of the object.

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  1. N

    Virtual and real image with concave mirror at 45 degrees

    I have a spherical concave mirror with focal length of 65cm, radius of curvature of 130cm. I hold the mirror close to the eye at approximate 45 degrees and I reflect an object below it as shown in the image. The distance between the object and the mirror is 90cm, that is more than the focal...
  2. navneet9431

    B Where will the image be formed?

    Suppose light rays from an object fall perpendicular to the surface of the plane mirror. Will the image be formed at +infinity(a virtual image) or -infinity(a real image)? I will be thankful for help!
  3. barryj

    Calculation about virtual image

    Homework Statement See my attached information Homework Equations On my attached solution The Attempt at a Solution see my attached sheet Please see my attached write up. I would appreciate a quick nudge as stated.
  4. S

    I HUD; virtual image at infinity

    Hi, I am trying to create an HUD display - basically create a virtual image at infinity and look at it. I have two plano-convex lenses; the distance between them is the sum of their focal lengths; my object is therefore imaged at infinity. Here is the schematics that I'm pretty much trying to...
  5. W

    Using Norton Ghost to Copy VM Setup?

    Hi all, There is a VM setup at work that I would like to copy into my home PC. Would Norton Ghost be able to do the job? Are there other ways ( A VPN is not an option, just in case)? I am just curious, since the VM is itself just software, why is it not possible to just save it as a file and...
  6. S

    Is the idea of negative absolute temperature analogous to a virtual image?

    Is the idea of negative absolute temperature analogous to a virtual image in geometrical optics? I was reading this article about such a negative temperature: http://www.livescience.com/25959-atoms-colder-than-absolute-zero.html It seems to me that since temperature is defined by its...
  7. N

    A Basic question about Head-Up Display and Near Eye Display

    I have seen built-in HUD in both a BMW and a Mini Cooper. In the first the windshield is used as the combiner while in the second they use a separate piece of glass located on the dashboard. The systems work by reflecting and magnifying a real image at least once in order to create a virtual...
  8. S

    Virtual image size/distance in an OAP mirror

    These seems like an easy question, but I have found nothing online: Does the size and distance of the virtual image produced by an off-axis parabolic mirror vary as a function of the off-axis angle, or will it be the same as the parent parabola? Specifically, I am trying to create a simple...
  9. RabbitWho

    Understanding Focal Length: Solving for Image Position with 1/u + 1/v = 1/f

    Homework Statement u= distance from the object to the mirror v = distance from the image to the mirror f = focal length I don't understand what they are talking about and I would like to 2. Homework Equations If the image is real 1/u + 1 v = 1/f If the image is virtual 1/u - 1/v = 1/f The...
  10. RabbitWho

    Virtual image on the perpendicular

    Homework Statement The book ("Real World Physics") says A virtual image in a plane mirror is on the perpendicular from the object to the mirror Homework Equations I know that the normal line is perpendicular to the surface of the mirror And I know that the angle of the incidence and reflection...
  11. P

    Image of a virtual object by a plane mirror

    A plane mirror forms a virtual image of a real object placed in front of it and a real image of a virtual object placed in front of it. I can't picture the second case. Please show me a ray diagram showing real image formation by a plane mirror or just explain the case of real image formation by...
  12. T

    Displacement of virtual image problem

    An object is within a glass sphere of radius R with a refractive index of 1.5 . I'm trying to calculate the displacement of the virtual object relative to the actual when viewed from the side, such that the refracted ray emanating from the object becomes horizontal. I would like to know S (the...
  13. Max Matiauda

    Image formed from object at focal point of concave mirror

    The question posed: "An object is located to the right of a mirror that in concave in its [the object's] direction. If the object sits on the focal point of the mirror, what answer best describes the image formed?" Our class is united in the notion that as the rays would be parallel...
  14. S

    Can a real image be formed by a virtual image?

    That is, take the virtual image as the object for a second lens?
  15. O

    Virtual image and Virtual Object

    so virtual image is my image on the mirror? If that was true, then what is a virtual object? (with examples please)
  16. O

    Hand drawn ray tracing through an optical system

    Hi, I am familiar with drawing rays through a lens. But when a few lenses are put together, things become confusing to me. For example, if a first positive thin lens at 0 forms a real image 10cm away, what would happen when we put a second positive thin lens, say at 5cm along the optical...
  17. aleksbooker

    How do you calculate the location of the third virtual image?

    Homework Statement Two 3.0m wide mirrors meet at a corner. Taking the corner as the origin of the x/y axis, A red ball is placed at point A (-1m, -2m). 1) How many images are seen by an observer at point O? [Point O is not given coordinates, but looks to be at approximately (-3m, -3m)]...
  18. H

    Why is virtual image not seen when a defective eye is corrected?

    Hello Everyone! I have a question related to the ACTUAL APPEARANCE of the virtual image/object formed when a person wears a lens. When a lens (spectacle) is used for correction of vision to make the rays meet at retina, my book says a virtual image seems to form before the lens. This takes...
  19. M

    Location of a virtual image in a convexed mirror

    Homework Statement An object 2.71 * 10-2m tall is 0.14m in front of a convex mirror that has a radius of curvature 42cm. Calculate the position and height of the image, is the image inverted or upright? Homework Equations Well, I've stated that I'm using the ray model of light. As far...
  20. J

    Why is it possible to see a real image in a mirror?

    I am having trouble understanding how mirrors have only either a virtual image or a real image. Take a concave mirror for example. If the object is placed between the mirror and the focal point, then there is a magnified virtual image. If the object is placed between the focal point and the...
  21. L

    Solving a Virtual Image Problem Involving a Converging Lens

    Homework Statement A converging lens of focal length 0.246 m forms a virtual image of an object. The image appears to be .933 m from the lens on the same side as the object. What is the distance between the object and the lens? Homework Equations 1/f = 1/di + 1/do Since the image is...
  22. M

    How to Calculate Focal Length of a Convex Mirror?

    Homework Statement The virtual image produced by a convex mirror is one-quarter the size of the object. b) What is the focal length of this mirror? Homework Equations 1/di = 1/f - 1/do The Attempt at a Solution i found di to be -9.3 cm but when i solved for f i keep getting it...
  23. R

    Mirror Optics- Measuring Virtual Image

    Recently, I asked my physics teacher how to measure the height of a virtual image behind a concave mirror. He said he wasn't exactly sure so he offered to give extra credit to anyone who could find information on how to do it. Is there anyone who can help?
  24. G

    Can Real Images Be Viewed Without a Screen?

    I have a question about lenses and mirrors and the above topic.. As I understand it, a real image is one that formed when all the light from one source is converged again at another point and our eyes see that light again spreading from the converged spot. So if you put a screen at the spot...
  25. I

    Calculating Distance from Mirror for Virtual Image Height of 1.145 cm

    Homework Statement An object whose height is 0.375 cm is at a distance of 10.5 cm from a spherical concave mirror. Its image is real and has a height of 1.145 cm. Calculate the radius of curvature of the mirror. Correct, computer gets: 1.58e+01 cm ACTUAL QUESTION How far from the...
  26. R

    Why cant we obtain a virtual image on a screen?

    If we can see a virtual image, why can't we obtain it on a screen?
  27. E

    Calculating the Diameter of the Moon's Virtual Image

    1. The radius of Earth is 6.40 x 10³ km. The moon is about 3.84 x 10^5 km away from Earth and has a diameter of 3475 km. The Pacific Ocean surface, which can be considered a convex mirror, forms a virtual image of the moon. What is the diameter of that image?2. 1/p + 1/q = 1/f M = h'/h = -q/p...
  28. J

    Concave mirror and virtual image

    we used a concave mirror and a candle for an experiment when the candle wa placed between the vertex and the focus of the mirror (f=12.7cm) a virtual image appeared behind the mirror. We measure the image distance approximately by pointing a finger towards where the image might be and got...
  29. J

    Calculating the Radius of Curvature of a Distant Tree's Virtual Image

    Hi; Could someone please help me with the following question: The image of a distant tree is virtual and very small when viewed in a curved mirror. The image appears to be 18.8 cm behind the mirror. What is its radius of curvature? (Use positive for concave and negative for convex). Would I...