# plane mirror can form real image...true/falseif ans is true i need explanation.

Ashwin Muralidharan IIT Madras
290 Points
12 years ago

Hi Suchita,

A plane mirror, if the object is not at infinity, can never produce a real image.

But yes, a plane mirror can produce real image under certain special cirumstances.

Just as a pinhole camera produces a real image. Take a small piece of a flat mirror (you can tape over a mirror leaving just a small clear area) and use it to reflect direct sunlight to a shaded screen. There will be a slightly blurred real image of the sun. You can draw a ray diagram to show that this works. Rays from the sun converge on the mirror piece and are reflected to the screen at angles according to their angles of incidence. Whether you can actually see this amount of light is another question. The smaller the mirror is relative to the reflection distance, the sharper but dimmer the image is. And since the projection screen must not shade the mirror, the image will be offset from the incident rays and the image may be distorted as a result.
It can be argued that both the pinhole camera and this setup, having an undefined focal point, only make approximations to an image. But there is a visible, recognizable projected image.

As an image is formed on a screen (we conclusively say that it is a real image, as only real images can be caught on a screen)

You can heve a look at some of the pictures on this site (where the experiment is set-up):

Hope that helps.

All the best.

Regards,

Chetan Mandayam Nayakar
312 Points
12 years ago

(1/u)+(1/v)=(1/f)

for plane mirror,f is infinite

therefore v=-u, and in addition u is always positive

therefore v is negative implying that image is always virtual