Mirror Image and Object are Equally Far from the Mirror
Scenario
Light from the LED that is reflected at A reaches the eye. → nerves on the retina sense the light + transmit electrical signals to the brain Brain → interprets that the light comes from inside the mirror (see the black dashed lines in first figure)
Do you think that the light ray in figure 1 is the only light ray the eye can see? → as shown in second figure → pupil is an extended opening that allows a bundle of light rays to reach the retina. → 2 rays shown are the limits of the bundle of rays that can enter the pupil. Any ray from the LED that reaches the mirror between A and B will be received by the eye and sensed by the brain.
To the brain → rays reflected off the segment AB on the mirror to the eye seem to be coming from the intersection point X. Hence → brain interprets that X seems to be where the LED is located. What we see in the mirror at X is called the mirror image of the LED.
Can you show that → can you go on to show that the perpendicular distance of X from the mirror is equal to the perpendicular distance of the LED from the mirror.
Law
Image of a point object in a plane mirror is always as far behind the mirror as the object is in front of the mirror
Scenario
Surface of a piece of paper is rough.
in the image → 3 examples of reflections of rays from the LED are shown. → each reflection points to a different location where the LED seems to be at. → brain cannot interpret where the image is. → Tiny point source of light looks like many point sources that are at different locations (images 1 2 and 3) after reflection → there is diffused reflection. hence a piece of paper with uneven surface cannot form a mirror image.
Mirror Image is Virtual
mirror image is called a virtual image and it is a three dimensional virtual object
Mirror Image and Object are of the Same Size
Virtual mirror image of an object refers to the set of imaginary points that are as far behind the mirror as the corresponding points of the object are in front of the mirror. → hence mirror image is always the same size as the actual object, provided that the mirror is a plane mirror.
Note: size of image depends on the observer. Position of the observer looking at the image and object plays a part in the perception of the size of the virtual image.
Note
When we look at 2 identical objects → they might not seem the same to be of the same size if they are placed at different distances from us. → object that is further away looks smaller. → thus mirror image seems smaller because the observer is further from the mirror image than the woman
Mirror Image is Laterally Inverted and Upright
Image is described as Laterally inverted and Upright
Summary
- Image and object are equally far away from the mirror
- image is virtual
- image and object have the same size
- image is laterally inverted
- image is upright
Important
Imagine you are standing in front of a mirror. What is the shortest height the mirror must be to see your entire body in the mirror? -To see your entire self in a mirror, the shortest height of the mirror should be half your height. This is because the mirror reflects light symmetrically, allowing you to see your full body even if the mirror is only half your height.>