Fintan stands in front of the bathroom mirror. His image seems to stand behind the glass, inside the wall, where there is no light at all. What is his eye actually seeing?
A plane mirror's image is virtual: that was stated last lesson. This lesson explains why, with one drawing you will use for the rest of the topic.
Light from the tip of Fintan's nose spreads out in every direction.
Two of those rays strike the mirror and reflect into his eye, each obeying the law of reflection.
After reflecting, the two rays that enter his eye are spreading apart: they diverge.
An eye receiving diverging rays traces them straight back to find where they came from.
Traced straight back through the mirror, the two lines meet at one point behind it.
No light ever travels behind the mirror to that point; only the traced-back lines meet there.
In a ray drawing, the traced-back lines are drawn dashed: a dashed line means the eye's trace, never a path light takes.
You can still see a virtual image perfectly well, because real reflected rays really do enter your eye.
What a screen cannot do is catch it, because no light arrives behind the mirror.
Greer sees a mug's image behind a plane mirror. Explain where the image point comes from.
Rays from a point on the mug reflect off the mirror and enter Greer's eye, diverging.
Her eye traces the diverging rays straight back.
The traced-back lines cross at one point behind the mirror.
No light travels to that point.
The image point is where the traced-back lines cross: a virtual image.
A plane mirror hangs on a stand in the middle of a room, and a lamp's image appears 1 m behind it. Haldis holds white paper at that spot, behind the mirror. Why does the paper stay dark?
The reflected rays leave the mirror on the lamp's side; they never cross into the space behind the mirror.
The image point is only where the eye's traced-back lines meet.
No light arrives at the paper.
The paper stays dark because no light ever travels to the image point.
Reflected rays from a plane mirror reach Elowen's eye spreading apart. Where does she see the image point?
Greer says: 'A virtual image cannot be seen with your own eyes.' Is Greer correct?
Haldis says: 'No light ever travels behind the bathroom mirror to the place where your image appears to stand.' Is Haldis correct?
Why is a plane mirror's image virtual?
In a ray drawing of a plane mirror, part of a line behind the mirror is drawn dashed. What does the dashed part show?
A lamp stands in front of a plane mirror in an otherwise empty room. Through which region does the lamp's reflected light actually travel?