• 
• 1 answer

A thermocouple produces a tiny voltage proportional to the temperature difference between two junctions where dissimilar metals meet.

<><><>

Thermocouples use rare-earth metals (chromium, aluminum, nickel, etc), usually in pairs. As these metals heat up, they react with one another and one metal sheds off an electron, which is then seen as electricity. Thermocouples usually produce a very small amount of electricity, often only enough to operate electric 'gates'.

• 
• 1 answer

(Frequency) x (Wavelength) = Speed of light.

Note carefully that the "speed of light" in the equation above is the speed of light in the medium that the wavelength is measured in. In vacuum it will be the famous constant "c", but when light travels through any sort of material it's speed is slowed and its wavelength shortened by a factor called the refractive index of the medium. Because wavelength and speed are reduced by the same factor the equation still holds. Light's frequency is not affected by the medium.

• 
• 1 answer

alessandro volta

• 
• 1 answer

electromagnetic waves are produced by the changes in the sub atomic level when heat or electricity is applied to an atom electron which is present in lower energy level will obsorbs energy and jumps in to higher energy level after that it again jumps in to lower energy level.when the electron is jumping in to lower energy level it emitts energy in the form of photons.these transmission of photons is said to be electromagnetic waves.in the electromagnetic waves electric and magnetic fields are perpendicular to each other and also perpendicular to the direction of wave propagation.

EM waves can also be produced by the action of a radio-frequency current in an antenna. Radio transmitters produce power at a single frequency and the antenna acts as a tranducer taking the power from the transmitter and converting it into power that is radiated into space and can be received at a distant point.

• 
• 1 answer

There is continuing debates about "Non-Ionising Radiation" and the safety issues; although more particularly for cell phones and urban emitters rather then DECCA RADAR and DECCA Navigation emitters (note DECCA is the Chinese work for RADAR, comes from the British company that pioneered DECCA navigation). Non-Ionising Radiation is the kind of Radiation that does not strip Ions from bio-chemical bonds unlike other more harmful radiations like Gamma, Nuclear Radiation. RF radiation waves are Non-Ionising, however specific frequencies can be more readily absorb by some parts of the body then others. This is to do with resonant frequencies for body tissues and the one quarter wavelength in the RF wave it self. The rate of absorb-ion is known as the SAR (Specific Absorption Rate). The general recommendations are not to stare directly into RF beams or expose soft tissues for very long periods of time and short ranges to the emitters. Some medical practitioners believe that some frequencies have a risk at close ranges for developing cataracts etc. It is also important to understand that RF power lowers as a function of range by a "range squared law", so the power drops off quite quickly with range. Other factors are amount of exposure you receive (long term) and the frequency and power you are being exposed to (the dose). In the RADAR case it is also important to remember that they use high gain antenna, and this means that the radiation is mostly in one direction and much less in others. In the DECCA navigation emitter case the energy level is less power and is more omni directional. The RADAR case's concentrated beams maybe scanned and the RF Power maybe pulsed (not constant). The Radar beams should be arranged to not point directly into inhabitants at close ranges, and the specific range is dependant on the mean power scan rate and range against the frequency. RADARs are arranged in this way. In the DECCA navigation case the RF is Continuous, and given the range of properagation is quite far you would expect the power levels also to be much higher, however the frequency is quite low at 70 - 130 kHz and lower frequency propagate much better then higher ones so the power level can be much less. It is also believed to be much less harmful risk as these frequencies are far away from water and bio-chemical resonates. However, if you work with RF and/or RADAR it is impotent to remember that repeated exposure can harmful and that the Microwave Oven was discovered by a scientist that melted a chocolate bar in is pocket because it was in a radio beam at very close range. I do not now if he suffered as a result of it but I assume the chocolate bar was not consumed.

• 
• 1 answer

The radiation of thermal energy can occur in a vacuum. Radiation is accomplished by the movement of electromagnetic waves through the vacuum, like light. Light, and particularly infrared light, is often associated with the movement of thermal energy (heat) through a vacuum.

• 
• 1 answer

IR is heat in the form of electromagnetic radiation. The IR is absorbed by the food causing it to become hotter, eventually becoming cooked (or finally burning).

The Easy-Bake oven toy uses mostly the IR emitted from a 100W lightbulb to bake its small thin "cakes".

• 
• 1 answer

You can Stick to the formula which is :

wavelengths/secounds = Hz

so that

Frequency (Hz) = Wave speed (m/s) / Wavelength (m)

OR

Frequency (Hz) = 1 / Period (s)

• 
• 1 answer

AM.

• 
• 1 answer

The EM spectrum is the range of frequencies of EM radiation.

From low to high frequencies the spectrum goes: Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, and Gamma ray.

Frequency is inversely related to wavelength by c = frequency * wavelength where c is the speed of light. So the same spectrum goes from long wavelength to short wavelength

• 
• 1 answer

• 
• 1 answer

Isaac Newton discovered the visible spectrum of light while fooling around with a prism (from which is derived the basic principle of a rainbow.) He later wrote about his findings in his well-known book, Optiks. Isaac Newton was also a master of atsronomy, calculus, and physics. It was also he who "discovered" gravity when an apple fell on his head. It is also probable that this experience led him to discover the effect of concussions on dementia. OK, not really about the dementia part.

• 
• 1 answer

Yes, about 1000 times more.

• 
• 1 answer

• 
• 1 answer

The first modern semiconductor diode was made with germanium. These diodes were invented in ww2 for RADAR.

But before that semiconductor diodes were made with galena (lead sulfide), copper oxide, and selenium. I have no idea which was "first".

• 
• 1 answer

By definition, an isotropic radiator radiates equally well in all directions. A simple vertical whip would have such a pattern in the horizontal field.

• 
• 1 answer

• 
• 1 answer

Yes, out of all the colors of visible light, violet has the shortest wavelength.

• 
• 1 answer

Gamma rays have a quality factor of about one.

• 
• 1 answer

Bremstrahlung is German for "braking radiation." It refers to radiation that is associated with the positive or negative acceleration of charged particles. The energy of the emitted photon equals the loss of kinetic energy of the particle. Characteristic radiation refers to groups of discrete wavelengths characteristic of the emitting element.

• 
• 1 answer

GaXrUlViInMiRa. Done by the first two letters of each type of wavelength. The visible spectrum really consist of the colors but here is listed as "Vi."

Gallant X-rays ultimately violate interesting micron radios.

• 
• 1 answer

Sunscreen is used to protect the skin from ultraviolet radiation emitted primarily by our sun. The ozone layer also protects us from ultraviolet rays, however the current problems with holes in the ozone layer makes wearing sunscreen almost essential if one is going to be outside for an extended period of time.

• 
• 1 answer

The emission of laser beam through the semitransparent end face actually consists of spikes of high intensity emissions. This phenomen is called spiking of the laser.

• 
• 1 answer

X rays are are able to penetrate less dense materials easily, such as muscle and skin tissue in medical situations or plastics and wood in other applications.

As the material becomes more dense, the x rays penetrate less easily.

Materials such as steel or bone in a medical setting are more dense along with such materials as lead and tungsten in engineering situations.

• 
• 1 answer

The best physics project topics to study depends on what you find interesting.

If you find everyday things like motion, pendulums, and collisions interesting, study mechanics.

If you find things like optics, circuits, and electricity interesting, study electromagnetism.

If you find things like statistics, temperature, and entropy interesting, study thermodynamics.

If you find things like time dilation, the speed of light, and black holes interesting, study relativity.

If you find things like the universe, dark matter, and star formation interesting, study cosmology, astrophysics, and nuclear physics.

If you find things like particles, accelerators, atomic bombs and unified force theories interesting, first study quantum mechanics, then study nuclear and particle physics.

If you meant what are the best physics project topics to do as a science experiment, use the guidelines I stated above, but stick to the first three topics; mechanics, electromagnetism, and thermodynamics.