Tag Info

New answers tagged

0

It's quiet simple: The photon is absorbed by an electron, the direction of the electron's spin flips and sends a neuron to the brain. A lightbulb works the other way around: Electrons are forced to flip their spin and therefore they are emitting photons.


2

Although there are already some excellent answers, I believe they are a little complex. Please allow me to offer a simplistic answer. Let me start with the analogy of sound waves and the ear. The sound enters the ear and causes certain cilia to vibrate in response to the frequency and amplitude of the sound wave. Similarly a photon (as a wave), enters the ...


2

Photons are energy. When a photon hits your retina, that energy is absorbed and converted to electrical energy in your optic nerve.


6

Light from all over the place hits your eyeball fairly randomly. The lens forces light from a specific angle to hit a specific part of the retina. This HowStuffWorks article shows how the mechanics of that work. The only major differences between camera lenses and eyeball lenses is that we can dynamically alter the shape of the lens to focus on different ...


16

Photons can be created and destroyed freely, since they don't have charge or mass. Turn on a light, and you create many photons. Any body (made of atoms) not at absolute zero temperature will spontaneously emit photons. They are consumed just as easily. Most any bit of bulk matter will absorb a photon in the electrons on the surface, transforming the energy ...


4

Imagine a spring-loaded trap with a hole that's sized such that only a particular size of object can enter the hole and trigger the trap. The molecules involved in vision are like that trap, with a bond having an electron energy gap tuned to the visible frequencies of light, encapsulated in a specialized protein that transforms the absorbed energy into a ...


-15

Shortly, the energy of the photon goes over to the electron. But energy is a vague concept. In material sense, could the photon, or better, the electron's electric field and the electron's magnetic field be quantized? I developed a model with two different quanta. Photons, electrons, positron's, protons, neutrons, ... are made from this quanta. Photons are ...


27

From the wiki article on color vision as an illustration of how photons are absorbed: Perception of color begins with specialized retinal cells containing pigments with different spectral sensitivities, known as cone cells. In humans, there are three types of cones sensitive to three different spectra, resulting in trichromatic color vision. Each ...


1

Assuming you fix the temperature at the cell boundary, you can solve for the steady state temperature profile within the cell using (see any elementary heat transfer book) $$\nabla^2 T = -\frac{\dot q}{k}$$ where $k$ is the thermal conductivity on the inside of the cell and $\dot q$ is the heat generation rate per unit volume. The temperature only varies ...


0

The thermal conductivity for water is k=0.56 W/m⋅K,all right,but this is for a lake,for exemple,when the heat transfer is between the air and the cold-water layer.The unit of measurement is W/mK ,not W/(m^2)K. So it's for the thickness ,not for the surface! If you want to calculate the heat production in the time unit ,H,start from: H=4π(r^2)ΔT α ,where ...


0

More research confirms @DanielSank's comment. This plot shows the dynamics for a longer period of time (from Efficient estimation of energy transfer efficiency in light-harvesting complexes): As you can see, due to loss and trapping, the exciton population of site 3 decreases after some time, just as @MarkMitchison and @DanielSank mentioned.


1

If a human is physically incredibly strong, and can push up off the ground no matter the gravitational pull, then the maximum amount of gravitational force the person can push off in would make him walk the fastest. My reasoning behind this is if he/she has no trouble pushing off the ground, and all that matters is minimizing the duration the persons foot is ...


3

The Sievert is a derived measure of stochastic health risk. It's used only in cases of low dosage ionizing radiation. High dosages that produce deterministic health effects are measured in the Gray (Gy), a purely physical term which represents the actual deposit of one joule of energy in one kilogram of matter. Unlike the Gray, the Sievert does not ...


0

Quite simply, Absolutely not. You've stumbled on to an "idiotic weight loss" idea, that is already very popular. There are any number of ridiculous "products" available for this, from crowdfunding ... example idiotic product - crowdfunded to conventionally multi-level marketed idiotic products (just search "cold! weight loss!" or similar), and indeed any ...


3

Even when you're hot, the body keeps producing heat, which it then goes through the trouble of shedding. Unless you were already very cold, the heat to warm your water and food intake will come out of this surplus. The body may even save energy because it doesn't need to shed as much heat. If you're wiling to be very cold all the time, you can do so more ...


1

In addition to the feedback mechanisms mentioned in the answer by Chris Drost causing you to eat more or exercise less, there are also mechanisms that will directly lower the basal metabolic rate in case you don't eat more or exercise less. Let's consider some animal that lives in Nature and due to some changes in the environment it has to expend more ...


1

In biological terms, one talks of a "calorie deficit". This is the number of calories less than that needed to maintain the body at a constant weight. Eating fewer than this, or using more calories by exercising will lead to weight loss. The Mayo Clinic [1] gives a figure of 1 pound of body fat lost for every 3,500 calorie deficit (32,000 kJ of deficit for 1 ...


44

Sort of, yes. Ice water is, in fact, a negative-calorie foodstuff and could be used to lose some weight. Fats contain about 37 kJ/gram of energy, drinking one glass of ice water will burn about 37 kJ or up to three times more if you eat some crushed ice as part of drinking the water: so that's 1 gram of fat burned per drink, up to 2-3 if you eat ice. The ...


4

The body surely needs to produce energy to heat the water one drinks - and it will heat water because almost everything in the human body is about 37 °C - but whether one loses weight in the process depends on whether the energy is taken from the accumulated fat, or from piles of extra food one devours because he or she is hungry and can't resist. ;-) The ...


0

Measure first, think later. The best tunnel for experiencing ear discomfort around here is a train tunnel under a canal, the Drontermeertunnel. The graph shows the air pressure recordings I made in the train. A and B are the gates of the tunnel. Orange indicates when I experienced ear discomfort (although it wasn't easy to decide when discomfort started and ...


2

Run this to determine which frequency range(s) you can hear http://onlinetonegenerator.com/hearingtest.html If you can hear 14kHz-15kHz then the problem is with the radio or transmitter otherwise it is your hearing I imagine that loss of hearing at an intermediate frequency would be rare especially if it is in both ears. My bet would be with poor speaker ...


1

Considering light travels at relativistic speeds much faster than you can in your car, the exposure is the same. The same logic does not apply as for rain as rain doesn't fall at relativistic speeds.



Top 50 recent answers are included