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Questions tagged [perception]

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88
votes
4answers
13k views

Why does a yellow object turn white under a yellow light? Shouldn't it turn yellow instead?

Recently I was eating a yellow rice for lunch in a restaurant with only yellow lights. But the rice looked white! I was intrigued by this because I always thought it should look yellow since the ...
77
votes
8answers
8k views

Does quantum mechanics play a role in the brain?

I'm interested in whether the scale of processes that occur in the brain is small enough to be affected by quantum mechanics. For instance, we ignore quantum mechanics when we analyze a game of tennis ...
74
votes
5answers
7k views

Why can we distinguish different pitches in a chord but not different hues of light?

In music, when two or more pitches are played together at the same time, they form a chord. If each pitch has a corresponding wave frequency (a pure, or fundamental, tone), the pitches played together ...
60
votes
6answers
9k views

How does light combine to make new colours?

In computer science, we reference colours using the RGB system and TVs have pixels which consist of groups of red, green and blue lines which turn on and off to create colours. But how does this work?...
19
votes
9answers
9k views

Why do objects appear smaller when viewed from a distance? [duplicate]

Yes, I know all about perspective (I'm an artist). I even have some basic knowledge of descriptive geometry. I know how it works. My question is more about why it works. I have a sneaking suspicion ...
17
votes
5answers
7k views

Musical notes and colors of a rainbow

I have wondered that in an octave in piano there are seven primary notes, and also we observe mostly seven primary colors of a rainbow. I know we perceive logarithmically, that means we only care ...
16
votes
2answers
5k views

Why can't the human voice produce a Shepard tone?

Audio of a shepard tone on youtube. So what is a Shepard tone? A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played ...
15
votes
5answers
4k views

Why do we remember the past but not the future?

The question is sometimes referred to as the "psychological arrow of time" (Hawking, 1985). Here the past is understood as a moment or time when the entropy of the universe was lower, and contrarily ...
14
votes
10answers
851 views

How to explain (pedagogically) why there is 4 spacetime dimensions while we see only the 3 spatial dimesions?

I have been asked this question by a student, but I was able and in the same time incapable to give a good answer for this without equations, so do you have ideas how one can explain this in a simple ...
14
votes
2answers
4k views

Why does the sky suddenly look gray through this window?

I am looking to the windowed roof of my building, and I notice that the sky, which has few white clouds, sometimes looks completely gray, as if there was a huge cover of gray clouds, but there are not....
12
votes
3answers
18k views

What is the color of a mirror?

A mirror couldn't be white, as then you wouldn't be able to see your reflection so clearly. It wouldn't be transparent, as that then won't reflect. So what color is it?
10
votes
5answers
5k views

Why don't humans perceive sound waves as twice the frequency they are?

I was reading about how at how acoustic beats work. If we combine two waves with frequencies $f_1$ and $f_2$ and unit amplitude, their combination is $$ \begin{align} A &= \cos\left(2\pi f_1x\...
10
votes
2answers
18k views

How many frames can human eye see? [closed]

What's the limitation of our eyes? Can we differentiate 60fps from 120fps? Are new 144hz monitors just a marketing trick? Couldn't find any proper journals or studies about the matter.
9
votes
2answers
6k views

How do color filters placed in front of a light source,change the color of light that passes through?

For instance, placing a blue transparent folder in front of a desk lamp, makes the light that shines through it appear blue. From what I understand some red car lights do not have red light sources, ...
9
votes
6answers
37k views

Why do objects appear smaller when farther away?

Why does the apparent size of an object change when it is farther away from me compared to when it is closer to me? Can someone perhaps explain this through an optics perspective?
8
votes
2answers
189 views

Why does the additive color model use red, green and blue instead of yellow, green and violet?

Long cone cells in the human eye are most sensitive to 570-nm wavelengths which are more like spectral "yellow" than spectral "red" and short cone cells are more to 440-nm wavelengths which are more ...
8
votes
2answers
564 views

Why does the moon appear fairly flat to a naked eye?

When I look at the regular ball picture the "edges" appear somewhat darker. Here's a random image I just found on image search :) Image source and that's how I can tell it's "round". Or so I assume. ...
8
votes
4answers
8k views

Why does the human body feel loud music?

I was sitting close to a speaker and I could feel the sound coming from it all over my body, especially in my heart, and it pounded with the loud beats of the music. Was my heart pounding because of ...
7
votes
5answers
894 views

Perception of Depths and Stereovision [closed]

I watched a video on Youtube and read a few articles which say that human beings see 3D because we have two eyes. But does that mean when I close one of my eyes, I should see 2D? It doesn't happen so. ...
7
votes
3answers
355 views

Effect of layout on text visibility [closed]

My college recently switched to whiteboards. Though writing on a whiteboard with a black ink sounds similar to the conventional way of writing with white chalk on a blackboard, it feels very different....
7
votes
1answer
1k views

Why does the visible light spectrum appear to be circular [duplicate]

I'm not sure if this is an acceptable place to ask this question, as it may have more to do with the biological workings of human eyes than with the physical properties of light, but I'd rather hear a ...
6
votes
3answers
619 views

Why does the point of intersection of two shadows look brighter?

When I sit in my garden during the day I always keep looking at the two intersecting shadows of two rods. It looks something like this: What I find weird about it is that at the point of ...
6
votes
3answers
11k views

What happens to sound waves?

I apologize if this is a naive question, but I never really learned about this. I'm curious as to what happens to sound waves after they are "used"? For example, if I say something to you verbally, ...
6
votes
1answer
318 views

How is the perceived quality of sound measured and analyzed?

I am doing a physics experiment researching the effect of temperature inside the clarinet pipe on the quality of its sound. I know that the speed of sound is directly proportional to temperature of ...
6
votes
3answers
2k views

Why does the moon appear bigger close to the horizon, rising or setting? [duplicate]

Possible Duplicate: Why does the moon sometimes appear giant and a orange red color near the horizon? I made a little research about this and found this article http://en.wikipedia.org/wiki/...
6
votes
2answers
435 views

What frequency is the scratching of finger nails on a blackboard?

This is the frequency/intensity that sets my teeth on edge. Does anybody know what frequency (roughly) it is? I am guessing it is near the top of normal human hearing, 20kHZ, but I'm not sure if ...
6
votes
2answers
478 views

Is the color wheel just an optical illusion? [duplicate]

As a kid, I was taught that that blue and yellow make green, yellow and red make orange, and red and blue make purple - forming the subtractive color wheel. As an adolescent I was taught that blue and ...
5
votes
1answer
9k views

Why do we see brown light?

While researching about lasers (it's my hobby), it suddenly hit me: there are lasers for every color of the visible spectrum, but there are no brown lasers. Brown isn't even on the rainbow. How is it ...
5
votes
3answers
318 views

How does the human ear guess the source of the sound?

Suppose a sound is produced behind you. You can easily tell that the sound came from behind. Our ear lobes face towards the front and hence traps the sound waves which come from the front. Yet, we ...
5
votes
2answers
428 views

Why does the colour wheel wrap around?

Red colour bares 430-480THz and Violet bares 670-750THz according to Wikipedia. What frequencies are the colours between red and violet? Will they be higher than red? or lower than violet? What ...
5
votes
1answer
2k views

Why does the sky look darker blue directly above me, but get lighter in the distant sky?

it seems that the sky looks a bit darker right above me, but if I look into the distance, I see a paler blue.
5
votes
3answers
1k views

When does the wagon-wheel effect occur?

Sometimes you see a video of a fan or a propeller spinning very fast, and the apparent rotation is distorted. The fan can appear to be moving in the opposite direction of rotation, or even stationary. ...
5
votes
1answer
231 views

To what degree does guitar construction affects the vibration of the strings?

There's an old debate going on in the guitar community about how much does wood choice and body shape affect the sound of an electric guitar. No one denies that there's a difference acoustically (how ...
4
votes
3answers
3k views

Why we see upright images?

Since it's convex lens there in our eyes so image formed on our retina is inverted, so how come that we see upright images?
4
votes
1answer
433 views

Differences of waves in water and air

When one drops a pebble in a body of water, one can observe multiple waves emanating from the point the pebble came in contact with water. Be it because the water "jumps" up and comes back down, ...
4
votes
7answers
35k views

As 3-dimensional beings, do we really have 3-dimensional vision?

I was watching this video on YouTube of a high school student explaining perception in different dimensions, basically stuff he learned from reading the book Flatand. At one point in the video, he ...
4
votes
2answers
202 views

Human perception of temperature

I had the following thought experiment recently: Suppose we have a vibrating plate for which we can tune the amplitude and frequency of vibration, and imagine we hold a finger against the plate. For ...
4
votes
1answer
47 views

Astronauts in spacecraft, they have to circle the earth many times a day, do they also have the illusion of the moon?

Astronauts in spacecraft, they have to circle the earth many times a day, do they also have the illusion of the moon? I don't think they have, because according to the theory, the illusion of the moon ...
4
votes
1answer
245 views

Why do we experience a slice of time, but not a slice of space? [closed]

I (and every one I guess) perceive space as an extended region where things happen. In contrast, time is perceived as a lucky of slice. Also in space I can choose in which direction I want to move, ...
3
votes
2answers
364 views

Distance and Speed

When I look up in the sky and I see a plane moving and it's further away why does it seem to move so slow compared if a flock of geese flies over at same time and seems to travel faster?
3
votes
3answers
807 views

Why do we perceive time?

Since everything (at least what we observe) is travelling through the time in the same direction and speed why do we even perceive the time? Of course, there is the time dilatation, but it is ...
3
votes
4answers
316 views

Do our ears (or brain) only perceive periodic disturbances?

Through a little time spent using sound editors for this and that, I've come to notice that if I play any musical note 440 times per second, I hear an A, whose frequency is 440Hz. Then I tried with ...
3
votes
4answers
364 views

Does Free Will Theorem imply that quantum mechanics plays crucial role in our brain’s functioning (consciousness)?

Does Free Will Theorem imply that quantum mechanics plays crucial role in our brain’s functioning (consciousness)? Is opposite statement of Free Will Theorem right: If elementary particles have a ...
3
votes
2answers
439 views

Why might Roger Penrose argue that Godel's incompleteness theorem(s) suggest that consciousness is non-algorithmic? [closed]

This past March, when I called Penrose in Oxford, he explained that his interest in consciousness goes back to his discovery of Gödel’s incompleteness theorem while he was a graduate student at ...
3
votes
3answers
6k views

Difference between note and tone: which one has only one frequency? [closed]

What is note and tone both in physics and musical terms? Are the two used in different ways in the different fields or are they the same thing. Moreover, which one has only one frequency? Well this ...
3
votes
2answers
212 views

Can we see refraction of light in the air with our eyes?

Can we see refraction of light in the air with our eyes? I am asking that because every night I see that the light in the street moving little is that because of change in the air? I do not mean ...
3
votes
3answers
5k views

Why does the Sun appear larger during the sunrise and sunset?

Why does the Sun appear larger during sunrise and sunset compared to its size during midday even though its distance from the Earth remains fixed all the day? It is only during the Winter when the Sun ...
3
votes
4answers
236 views

Why can we 'make' new colors simply by adding wavelengths?

White light is always said to contain all the different wavelengths of light. Why, then, can we 'make' new colors simply by adding wavelengths? Is it just a matter of our perception, that, when two ...
3
votes
3answers
630 views

Why can colors be mixed? [duplicate]

We can combine colored light, creating other colors, at least in terms of visual perception. But how it the result physically "a different color" - if it is at all? Or is all this not a physical ...
3
votes
2answers
4k views

Do we see color with higher frequency first?

Out of the 7 colours of the rainbow, violet has the highest frequency and the smallest wavelength. Does this mean that our eye sees it first? If yes, then why? Does it travel at the same or higher ...