2
$\begingroup$

Apparently the plane mirror makes virtual images, and virtual images cannot be projected onto a screen. If you look below, it is?

Virtual Image projection

If the eye is basically a screen of rods and cones, then everything is a real image?

I'm guessing I'm wrong, but how?

Thanks

$\endgroup$
  • $\begingroup$ Of course you can! dotted photons will come backwards and make your virtual image. $\endgroup$ – evil999man Apr 19 '14 at 14:50
  • $\begingroup$ What is shown in the OP's diagram does not happen! $\endgroup$ – DJohnM Apr 19 '14 at 18:40
  • 1
    $\begingroup$ "virtual images cannot be projected onto a screen" is poorly worded; "a screen placed at the location of a virtual image will not show anything" would be less confusing... $\endgroup$ – DJohnM Apr 19 '14 at 19:27
  • $\begingroup$ @User58220 Sarcasm. $\endgroup$ – evil999man Apr 21 '14 at 15:47
3
$\begingroup$

Part of the confusion may be that, in your proposed experiment, there are two object-->optical element-->image processes going on. In the first, a plane mirror forms a virtual image of a real object. As explained well by others, this means that there are rays of light reflecting from the mirror that appear, (by assuming straight-line geometry) to come from an object behind the mirror. This image is virtual; the rays never actually get there; the mirror could be mounted on the face of a granite cliff! So we have a virtual image.

Now, you look "in" the mirror, and begin to process those rays of light. As far as you are concerned, the rays are coming from a real object; that's what a virtual image does! So the lens in your eye forms a real image on the retina of your eye, and the rods and cones start to send electrical signals to your brain

| cite | improve this answer | |
$\endgroup$
5
$\begingroup$

The light from the object has to fall on the screen after converging so that we can see the image on the screen.

When light coming from a distant object is converged to a point or spot on a screen by using a convex lens we see the image on the screen because light actually have fallen on the screen from the object after passing through the lens.

When the object is so close to the lens that the light from the object cannot be converged by the lens to a point on the screen but starts diverging, it appears that the light has diverged or come from somewhere from the same side of the lens where the object is. Thats why when you see from the other side of the lens where the screen is, you see the image of the object on the same side of the lens where the object is,which is virtual. You can't put the screen there to obtain that image because the light has never gone there after passing through the lens. It all passed through the lens to the other side but diverged.

But you can see the virtual image when you view from the other side of the lens where the screen is because the virtual image now becomes the "virtual" object for the lens in your eyes. A real image of that "virtual" object is formed on your ratina.

You can now think for mirrors..

For plane mirrors, you can't get the virtual image on a screen by putting the screen behind the mirror. The image that forms on your retina is the real image of the "virtual object" behind the mirror.

| cite | improve this answer | |
$\endgroup$
  • $\begingroup$ You must have spent a lot of time writing this answer! Phew! Thanks so much! ;) $\endgroup$ – Turbo Apr 20 '14 at 22:23
2
$\begingroup$

To understand this you must first be very clear on the difference between real and virtual images. Light leaving on actual, physical object is dispersing---the light energy from each point on the object's surface is heading off in many different directions.

A image is formed when light appears to be dispersing from a different spot. This can happen either because the dispersing light from the original was brought back together again and passes through the focal point and disperse from there, or because the rays were simply rearranged so that their apparent origin lies in a new place. The former case is a real image, the latter a virtual one.

Only in the real case do you have light coming together so that you can project a bright spot on a screen.

| cite | improve this answer | |
$\endgroup$
  • $\begingroup$ I'll have a think about this and see if there will be any other answers before choosing this as the correct answer. $\endgroup$ – Turbo Apr 19 '14 at 16:48
0
$\begingroup$

You put the screen in front of the mirror, right?

If so, that's because the reflected light isn't strong enough. Very few photons are enough for our eyes to perceive them, but not enough for generate images on the screen (yet another reflection for us to see).

| cite | improve this answer | |
$\endgroup$
  • $\begingroup$ What will happen if we do it in a dark room with a strong torch? $\endgroup$ – Kartik Apr 19 '14 at 14:54
  • $\begingroup$ You will see the real image. $\endgroup$ – Qianyi Guo Apr 20 '14 at 1:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.