Looking in the mirror

Classical Mechanics Level 3

When you look at yourself in a plane glass mirror, what do you see?

Details and assumptions:

The mirror is made of glass and is silvered on the back surface.
Don't consider reflections in your eye/other mirrors
Ignore total internal reflection(s), if any.

one image, not laterally inverted one image, laterally inverted two images, one laterally inverted and one not laterally inverted two images, both laterally inverted all other options are incorrect

3 solutions

Raghav Vaidyanathan
Apr 22, 2015

A real mirror has two reflecting surfaces, one is the glass surface itself and the other in the silver coating beneath it. Most of the light incident on the mirror goes through the glass and gets reflected by the silver layer. This is the bright image that we see. But if one observes closely, a secondary image is visible. This image is dim and is formed due to direct reflection of incident light from the surface of the glass itself. This secondary image is similar to the reflection we observe in window panes.

This is more of a "gotcha" question, and it depends on at least two more things

1) That the "plane glass mirror" has the silvering in the back of the mirror, like most mirrors. But not all. Some, like optical mirrors, have the silvering on the front surface.

2) That we ignore internal reflections inside the plane glass, which will give rise to additional images (however faint they may be).

Neither is mentioned in the statement of the problem.

Michael Mendrin - 6 years, 1 month ago

Yeah, no shit, you can't assume that and that's not a fair question.

Christien Hughes - 6 years, 1 month ago

Yes....this question never said that the mirror is thick enough for the ray to get refracted and reflected by silvered end.

Samarth Agarwal - 6 years, 1 month ago

I concede to your points. I will edit problem to avoid such confusions.

Raghav Vaidyanathan - 6 years, 1 month ago

What I see and what you see are not the same. As the question had not mentioned in caution but rather eliminating contribution of facts although not all, I don't think answer as a normal person is incorrect. The person who describes the question should be blamed.

If I have selected the special answer, then I may have agreed with the answer; to be honest with you. However, I think you can only give praise to special answer but not to give a false penalty to ordinary answer. I suggest that both can be a correct answer. Some questions ought to have several answers!

Contrast and advancement of biological sensors and processors are important. As a tinnitus patient, I can tell you how my hearing is ignoring the noises by advance ignorance. Previously, there was someone in brilliant who ignored stereo effect of eyes and keep on saying that one can only see 3 faces of a cube at once. Many people do not rely onto computing to do maths but keep on with method of 19th century. In mandarin, we say if we believe that a thing exists then it does exist but not at all to a person if one doesn't believe.

We are not robot. Although the physics actually tells the truth of giving two images, as long as I didn't see and therefore not realizing it, WHAT I SEE BY EYES IS NOT EQUALS TO THE TRUTH! As I can only see one image on the mirror in my bed room before answering this question, I think no one should posses the right to over-write my finding.

Lu Chee Ket - 5 years, 8 months ago

Stereo eyes is a combination of two pictures into one: Two becomes one; this is a process. Eyes other than sight sighted, several images can appear to some people who do not wear spectacles. But generally, everyone deserves for a 2 in 1 for stereo vision. This tendency is a sort of power to cancelling away multiple images!

Lu Chee Ket - 5 years, 8 months ago

The question should be based on pure logic rather than observation. The thought of a second image will never come unless you have experienced it. The problem lacks clarity on these issues.

shuvam jaiswal - 6 years, 1 month ago

As far as I know, the image is not inverted laterally but rather "front to back" or perpendicular to the plane of the mirror. I guess that depends on your definition of "laterally", but I think that the most common perception would lead to the answer being "all other options are incorrect".

João Pereira - 6 years, 1 month ago

I up voted for this though. There is a reflection inside but I totally ignored them because the question told. Where more than 2 answers is also possible despite dimmer, answer of 2 cannot be the answer.

Ordinary answer should also be correct bah.

Lu Chee Ket - 5 years, 8 months ago

Manvith Narahari
Jun 4, 2015

Technically, there are a lot of images produced since after reflecting off the silvered back, there is a faint internal reflection off the glass. This reflection off the glass will then reflect off the silvered back again and the process will continue (with a transmitted and reflected ray being produced each time a ray hits the glass).

Could a rarer medium reflect the light back into denser medium?

suneesh jacob - 5 years, 11 months ago

Yes it can. Otherwise, the phenomenon of total internal reflection wouldn't exist.

Manvith Narahari - 5 years, 10 months ago

Is it not the denser medium reflecting light into rarer medium (reverse phenomenon) happening in case of total internal reflection?

suneesh jacob - 5 years, 10 months ago

Nilesh Nayan
Apr 23, 2015

I thought a different way. When we look in the glass actually we can also see an image on our eyes(when light is sufficient). So there are more than 2 images possible!

Yes, I thought people might do this. I will edit question to inform the reader as to not consider this fact.

Raghav Vaidyanathan - 6 years, 1 month ago

I even thought more differently that our eyes make image inverted and real on the inner side of eye and then the brain manipulates the image and makes it again inverted so to match the present condition........

Saurabh Patil - 6 years, 1 month ago

Looking in the mirror

3 solutions

0 pending reports