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As we know that concave mirror forms a real image when object is placed beyond focal plane. This image can only be seen if a screen is kept at the point of intersection of rays(sharp image).If any screen is not kept then we are not able to see the image formed by meeting of rays.Whereas in case of virtual image we don't need any screen .Our eyes sense the rays coming (appear to be coming) from image source and we see image.so why do we need screen to see real image even though the rays are actually meeting at a point then also we are not able to see image without screen.In the following figure we need screen for a,b,c,d and e.

image formed by concave mirror

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    $\begingroup$ I think you've got it backwards: a "real image" is one that forms at a specified image plane (location). Our eyeball, thanks to its own set of optics, can produce a real image on our retina for a variety of real or virtual object locations. $\endgroup$ – Carl Witthoft Apr 2 '14 at 13:17
  • $\begingroup$ We only ever see real images - formed on our retina. $\endgroup$ – M. Enns Jul 24 '17 at 14:02
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A real image can be viewed on a screen, a virtual image can not. Rays from both types can enter your eye, be refracted by your eye's lens and form a real image on your retina as @CarlWitthoft points out.

So it is not the case that a real image must be viewed on a screen. It can be viewed on a screen.

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  • $\begingroup$ I didn't understand your words must be, can be. I think you must need a screen to view a real image. Could you please elaborate. How do you think real image can be viewed without scree? $\endgroup$ – Immortal Player Apr 2 '14 at 15:47
  • $\begingroup$ That means if screen is not there then also we can see real image, but I have never observed a real image without a screen during my high school practical. Why is it so please explain. $\endgroup$ – user40999 Apr 2 '14 at 18:30
  • $\begingroup$ @user40999 If you've ever used a refracting telescope, you have. Somewhere inside the tube of the telescope a real image is formed. Rays continue past (or perhaps through) that real image, are collimated by the eyepiece, and then your eye's lens forms another real image, this one on your retina. $\endgroup$ – garyp Apr 2 '14 at 20:45
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    $\begingroup$ @GODPARTICLE For a point source object forming a real image, all rays converge to a point image. If you put a screen there, you will be able to see the convergence of those rays. If you don't put a screen there, the rays will continue past the image, and diverge. Similarly, rays diverge from a virtual image. Once the rays are diverging, there's no way to tell if the source is real or virtual. It is possible to use a screen to find the real image, but you don't have to. The image still exists whether or not you put a screen there to help see it. $\endgroup$ – garyp Apr 2 '14 at 20:59
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The answer is that you do not need a screen to view a real image as is explained here.
A real image is there whether or not a screen is present.

The difficulty when trying to observe a real image without a screen is focussing your eye on the image which is located in a region (in the air) with no points of reference.

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No, real images cannot be seen without a screen. in a refracting telescope after passing through the objective lens, the image is not seen as the eye piece lens forms a virtual image which does not require a screen.

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  • $\begingroup$ This isn't correct. While most compound optical systems don't have the user observe a real image directly, that doesn't mean it's imposssible. $\endgroup$ – rob Jul 24 '17 at 13:31
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    $\begingroup$ Look at the concave surface of a spoon. See that little upside-down image of you. It's real. No screen. $\endgroup$ – M. Enns Jul 24 '17 at 14:01

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