Physics regards the physical aspects of the natural world. It includes topics that deal with forces on different bodies within the universe and phenomena that explain how the universe works.

508,091 Questions

Why is the sky blue?

Sunlight interacting with the Earth's atmosphere makes the sky blue. In outer space the astronauts see blackness because outer space has no atmosphere.

Sunlight consists of light waves of varying wavelengths, each of which is seen as a different color. The minute particles of matter and molecules of air in the atmosphere intercept and scatter the white light of the sun. A larger portion of the blue color in white light is scattered, more so than any other color because the blue wavelengths are the shortest.

When the size of atmospheric particles are smaller than the wavelengths of the colors, selective scattering occurs-the particles only scatter one color and the atmosphere will appear to be that color. Blue wavelengths especially are affected, bouncing off the air particles to become visible.

This is why the sun looks yellow from Earth (yellow equals white minus blue). In space, the sun appears white because there is nothing in between to scatter its white light.

At sunset, the sky changes color because as the sun drops to the horizon, sunlight has more atmosphere to pass through and loses more of its blue wavelengths. The orange and red, having the longer wavelengths and making up more of sunlight at this distance, are most likely to be scattered by the air particles.

The scattering of visible light by atmospheric gases is most correctly called the Tyndall effect, but it is more commonly known to physicists as Rayleigh scattering after Lord Rayleigh, who studied it in more detail a few years later. Rayleigh Scattering is where red, orange, yellow, and green are passed through and blue, indigo, and violet are "scattered" out creating the color.

Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.

(*As for why the sky does not appear violet -- the wavelength most scattered -- see the explanation at the related link below.)

Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.
The sky appears blue to us because of the scattering of the blue light component of the light from the Sun. Some alpine lakes also appear a quite light blue colour for the same reason, light is scattered by tiny suspended flakes of minerals in the water.
Because the water particles in the air split the light and Blue light is dispersed the furthest that's why it creates the illusion the sky is blue

How do you use attenuation in a sentence?

After his heart transplant, he was given special medicine to prevent rejection, these drugs are to be taken daily in order for attenuation to take place and to attenuate the immune response and to keep the body from rejecting its new heart.

Installing this new piece of equipment will let through the lower frequencies, therefore achieving attenuation.

Which science is the most complex chemistry or biology or physics?

The most complex science between the 3 is biology followed by chemistry and next is physics.

This is because Biology as a science encompasses the nature and laws of life (scientifically), which means that as a science that studies life it ranges from the microscopic to macroscopic level of understand and acquiring knowledge about life. Biology in microscopic level includes the study of the cells, its components and the macromolecules that makes up for each components , how they work and what makes an organism alive up to the macroscopic level that includes the ecology understanding how organism interact with each other and with their environment, how environmental changes drives evolution and how evolution changes the way life goes with the living organisms. Hence, biology includes both understanding the science of chemistry and physics.

What device or instrument is used to measure air pressure?

There are several options depending on the type of air pressure being measured:

  • In the 1800's ships used a weather glass - a simple barometer - to measure changes in air pressure.
  • To measure atmospheric (ambient air) pressure, a barometer is used. (It may be either an aneroid or a mercury type of barometer.)
  • For tires, it's a tire pressure gauge.
  • In industrial processes and boilers the gauge is frequently called a manometer.
  • For pressure vessels it is a Bourdon gauge.

What is the movement of organisms from one place to another?

In the living world, the movements are diverse. The movement of animals is a migration. For example, there is seasonal migration of migratory birds or vertical migration of soil insects. The movement of single-celled organisms is a taxis (movement of the entire body to or from the stimulus). Movement is not always associated with the ability to move, so the pollen of plants is carried by the wind or insects. Cell movements are most often associated with the organelles of movement (flagella, cilia), but they can also move passively or with someone's help.

What is the Example of digital quantity?

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How does the tubelight on a vendor's cart work?

  1. a short circuit is brought about when short cut is provided for the current flowing there a as a result current bulb up the dangerous the electro-magnet coils are clus wonder and there is a chance of short circuit hence wire is to be inssulated so no electric currrent stops across and no short curict will be produced

Which term describes the tendency of an object to resist a change in motion?

An object's tendency to resist a change in its state of motion is called inertia. This is the basis of Newton's Laws of Motion; "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.". The state of motion refers to the object's velocity, which is the the speed and direction. One quantifies inertia as the quantity of mass of an object. On can say that the mass of an object is a measure of how much an object resists change in its motion. The more mass an object has, the more inertia it has. That's why it is harder to push a 3 ton box as opposed to a soccer ball, or something lighter.

What is the speed of ultrasound waves in the air?

The speed of ultrasound waves in a particular medium varies from 330 meters per second (m/sec) in air to 1450 m/sec in fat, 1570 m/sec in blood, and 4080 m/sec in the skull. Hence, ultrasound travel through the air with speed of 330 m/s.

Science investigatory project of avocado leaves?

You can try to find a use for avocado leaves like observing if it is good at repelling mosquitoes or if it will make a fire last longer or something like that.

Why does water have a high and specific heat capacity?

In simple words, water has high heat capacity because it has a lower molar mass, and specific heat is inverse to a substance's mass. Another reason for high specific heat is its strong hydrogen bonding.

What instrument measures temperature?

Most commonly, a thermometer.

Related Information:

Thermometers are used to measure the increase or decrease in the temperature of a system as it gains or loses internal energy.

An alcohol-in-glass thermometer has been the most common personal instrument used to measure temperature. Mercury thermometers are still around but are no longer offered for sale. Today, digital devices are available that scan the forehead or ear. Some other devices used to measure temperature are:

Radiation pyrometer, for extremely high temperatures;

Glass thermometer: mercury or alcohol;


Thermistor (thermal resistor)

Bimetallic strip;

Bimetallic spiral;

Platinum resistance thermometer (a resistance detector);


A mercury in glass thermometer uses mercury liquid contained within its glass structure to be subjected to heat.

the heat causes the mercury fluid to expand along the glass tube

and the total amount of expansion can be seen as a measure

along the accurate scale of indication.

This is a direct indication of the effects of temperature.

A more complex method of measuring temperature could be a

thermocouple measuring device.

A thermocouple consists of 2 dissimilar types of metal materials in the form of wires , which are joined at 1 end by weld/ fusion.

this single joined end is called the hot junction. The other end of the 2 wires are then terminated at separate junctions;

as in a electronic terminal block. This end of the 2 wires can be called the cold junction.

For most accurate temperature measure, I think temperature sensor is the first choice.

What kind of a simple machine is a toothbrush?

A toothbrush is not a simple machine, it does not work on the principle of levers, effort, and load.

It's not a machine at all in mathematical terms. A "machine" is that which performs "work", i.e. transfers or converts energy.

You arm moving the toothbrush is a machine by this definition, however.

Why are light and heat not considered matter?

Matter has mass and occupies volume. Heat, light, and other forms of electromagnetic energy do not have measurable mass and can't be contained in a volume. Matter can be converted into energy, and vice versa.

What is mass divided by weight?

Answer #1:

It's (1) divided by (the acceleration of gravity in the place where that mass has

that weight):

weight = mass x g (where g is the acceleration due to gravity)

⇒ mass/weight = mass/(mass x g)

= 1/g

On the earth, g ≈ 9.81 ms-2 ⇒ mass/weight ≈ 1/9.81 ms-2 ≈ 0.102 m-1s2

On the moon, g is approx 1/6 that of the earth, ⇒ mass/weight ≈ 6/9.81 ms-2 ≈ 0.612 m-1s2

If the questioner really meant weight divided by mass it gives the acceleration

due to gravity in that place otherwise I'm not sure of a use of knowing the

reciprocal of the acceleration due to gravity that the questioner asked.


Answer #2:

If you ask a scientist, that's true answer in the sense that a mass M experiences

a gravitational force Mg and if you measure weight in units of force (which

nobody does). But anyone else would be surprised to learn that a mass M (say

10 grams) would have a weight of anything else but M grams (10 grams).

Sometimes expressed as "grams weight" often just grams for short. If you pick

up a Kilogram, even a scientist would say "its weight is 1 kilogram". The

gravitational force on it is 1g, so if you let it go it will accelerate at a rate force

over mass, which is g. So the answer depends on your units of mass and weight.

That's why science lessons tend to avoid use of "weight". In outer free space

mass would be measured by (say) tension in the string if you whirl it on the end

of it around your head, but the weight (measured by a spring balance) would be

zero (precisely as described in the first answer above, with g=0).


Answer #2.1:

The problem with discussing mass and weight in the same units, and the reason that this masked contributor is waging a one-man battle to make the distinction recognized and acknowledged by users of this website, is the new problem that

you have now that the space age is here.

As long as we were all irrevocably bound to the Earth, one kilogram of mass would always weigh one kilogram, if you like it that way. We could afford to be sloppy about it, with hardly one out of ten men-on-the-street knowing or caring about the difference, and nobody ever had a problem with it.

But now that some of us have already slipped these surly bonds ... and among

the general population, the younger you are, the better the chance that you will

do so one day before you're done ... those who ignored the distinction begtween

mass and weight all through school, or never even encountered it there, are

poised to step into an inconvenient pile. Because as soon as you pack for your

trip to anywhere else away from Earth, and take along your lucky kilogram,

you're due for a shock when you step out at your destination: Your kilogram

doesn't "weigh" a kilogram there. It weighs something else. If you're on the

moon, for example, your kilogram weighs 0.165 kilogram ! That's the

shock I'm trying to avoid, because if you think the straight dope is too complex

for people to handle now, you haven't seen anything yet.

Matter attracts other matter does antimatter will repel the antimatter?

Antimatter observes and obeys the same fundamental forces that matter does:

  • gravity
  • electromagnetism
  • weak interactive
  • strong interactive

A positron, which is the anti-particle of the electron, for example, has the same mass as an electron and experiences the same attraction to all other matter (gravity) as an electron. That same positron is repelled by positively charged particles and attracted to negatively charged particles (electromagnetism).

Is it safe to take a shower during a thunderstorm?

No—in fact, the CDC encourages avoiding all water in your house during a thunderstorm. Your plumbing and the water coming out of it can conduct electricity if lightning strikes your home, and that can lead to you getting seriously hurt. Granted, this is a pretty rare occurrence, but experts still advise against it as an easy way to avoid something potentially fatal. You should wait half an hour after hearing the last boom of thunder before hopping into the shower.

What is dislocation density?

Dislocation density is the areal density of dislocations intersecting a plain, usually the free surface, given as number per cm2.

It may also be the volume density of dislocation line segments, given as the total length of dislocations divided by the containing volume (also 1/cm2), but this is rarely used in semiconductor physics, and more frequently found in engineering.

Dislocation density is typically measured by etching the free surface to form pits around the location at which the dislocation breeches the surface, and is termed etch pit density, or EPD.

Who invented the law of displacement?

The mathematician Archimedes of Syracuse.

The most common story (which was first told by Vitruvius but doesn't pop up in Archimedes' known works) goes that King Hiero II had a votive crown forged for a temple, and he supplied the pure gold the goldsmith was to use. However, when he got the crown, the King asked Archimedes to determine whether the goldsmith had used all of the gold supplied or substituted silver for some of the gold. Archimedes couldn't melt the crown down into a regular shape to find its density, because he had to leave the crown intact, so he puzzled over the problem for some time. While taking a bath one day, he noticed that the water level rose as he stepped in, and realized that he could use this effect to solve the problem, and supposedly ran through the streets screeching "εὕρηκα!" (heureka!, Greek for "I've found it!") naked. When he performed the test with the crown, he found that the goldsmith had indeed substituted silver for some of the gold.

Why are leptons divided into families?

Leptons are divided into three families with 4 particles (2 particles, plus their two anti-particles) in each family. In the electron family we have the electron, positron, electron neutrino and electron anti-neutrino. Each family has a higher mass than the one before it so the tauon is heavier than the muon which is heavier than the electron. The physical reason for there being three families is completely unknown and will probably win you a Nobel prize if you can figure it out!

Are quarks nucleons?

No, quarks are not nucleons. A nucleon is a term (in physics) that is given to either of the two component particles of an atomic nucleus: the proton and the neutron. Both protons and neutrons are composite particles from the family of hadrons, and hadrons are made up of quarks.