Electromagnetic Radiation

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".

The electromagnetic spectrum is called a spectrum because it consists of a range of electromagnetic waves or radiation, each with a unique wavelength and frequency. When these waves are arranged in order of their wavelengths, they form a continuous spectrum of different colors and energies.

Exit radiation refers to the electromagnetic radiation emitted from a material after an external stimulus, such as light or heat, is applied. This radiation can provide valuable information about the material's properties, structure, or composition. Exit radiation is commonly used in various scientific fields, including spectroscopy and materials science, for analysis and characterization purposes.

No, an object not moving relative to Earth is not a blue shifted object. With no relative motion, an object will not be subject to Doppler effect and will not red or blue shift. For an object to be blue shifted, the distance between the object and Earth must be decreasing. The object must be closing on Earth or vice versa.

No difference at all. Radio waves are one of many types of electromagnetic waves.

Wien's law is limited in that it is only accurate for objects that behave like blackbodies, meaning they absorb and radiate all incident energy equally. It also applies only to idealized objects that emit radiation in a perfect thermal equilibrium. Real-world objects may deviate from these ideal conditions, leading to inaccuracies in predictions made using Wien's law.

For pretty much the same reason that stars do. It's an optical illusion caused by the bending of light through a turbulent and hazy atmosphere.

If the unevenly-heated air between you and the streetlights happens to contain a mix of smoke, dust and water vapor, then the churning particles and droplets will act like tiny mirrors, shadows and lenses. This chaotic mix will distort the light rays passing through it, causing faraway light sources to appear to flicker or twinkle.

As you move closer to the light, the number of photons reaching your eyes rapidly increases. This tends to average out the apparent intensity of the light, making the twinkling effect 'magically' disappear. (This is also the same way ancient astronomers were able to tell planets from stars, by the way: the planets are close enough to Earth that it took a very turbulent sky indeed to make them appear to twinkle at all.)

Permanent magnets have a magnetic field around them. This field is an "area" of force, and the force is derived directly from the uniform motion of a large number of electrons in the ferromagnetic material. Moving electrons generate a tiny magnetic field around their path of travel, and this is the basis of the magnetic force. The "blocks" of atoms that have uniformly moving electrons are called magnetic domains. The aligned domains allow an "over all" magnetic field to be detected and even used by an investigator. The field will interact with ferromagnetic material to attract it, or will, when moved "past" any conductor, induce a voltage in that conductor.

A pair of magnets will attract or repel, depending on how they are held or placed. The magnetic field of each one will interact with the field of the other, and the lines of force will push or pull, as suggested.

Electromagnetic Waves do not require a medium, or matter to move through, to transfer waves. This includes radiowaves, microwaves, infared waves, visible light waves, Ultraviolet waves, X-rays, and gamma rays.

Any charged particle has an electric field surrounding it. If it oscillates, the electric field will continuously change, resulting in the production of a magnetic field, which is in phase with the electric field. But these two fields are perpendicular to each other. These two "oscillating fields" come together to form electromagnetic waves.

it protects all your internal organs from radiation by blocking the dangerous radiation, by producing sweat to protect against heat, has sensory receptors to tell you when you are in danger, and produce vitamin D from absorption of radiation

. . . wavelengths between roughly 380 and 750 nanometers.

From direct exposure to a massive dose of ionizing radiation, you can't. You can only pray that enough of your cells are left intact for you to survive.

However, ingested radioactive isotopes can be removed from the body by chelating agents, for example. But palliative care may be as much as you can hope for. Sorry.

The ozone layer in the stratosphere absorbs most of the incoming ultraviolet radiation from the sun. This absorption helps to protect living organisms on Earth from the harmful effects of UV radiation.

No, ultraviolet radiation has shorter wavelengths compared to visible light and infrared radiation. The electromagnetic spectrum orders radiation from longest to shortest wavelength as radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Basically it has to do with the blackbody spectrum.

Hot objects emit a broad spectrum of light, not just a single color. At the point where the temperature is such that the blackbody radiation peaks in the ultraviolet the overall spectrum is such that the emitted light appears to us as largely blue.

There may well be purple stars, but from our eyes, they appear blue. Our eyes, slightly deceive us.

See the related link for a picture of how our eyes perceive colour at a given temperature, and another for a video explaining in detail this question.

Our Sun would appear a kind of peach, if we had eye's better developed to a blackbody spectrum

Purple is a combination of blue and red. The light emitted by a star is of such a nature (black body radiation curve) that there is one predominate colour and lesser component of lower frequencies. (Higher frequencies are rapidly attenuated.) It is therefore impossible to get two colour emission peaks in both the blue and red of equal intensity - consequently no purple stars.

However you could have two stars closely orbiting each other: one blue and the other a red super giant, that at a great distance would look like a purple star, or a red star with a super hot white dwarf, that would work too. Interesting to note, the star Algol might fulfill this combination.

Yes, electromagnetic radiation weakens as you move further away from the source because it follows the inverse square law, which means the intensity of radiation decreases with the square of the distance from the source. So, the further you are from the source, the weaker the radiation will be.

Sunsets have always captured the imagination with their brilliant Calvin more so when people discover that sunsets vary depending on location, or when they discover an unusual or especially colorful sunset. Sunsets in the desert tend to be very orange, whereas the sunsets in urban areas tend to be muted and may have other colors like yellows and reds. But, whether in the deserts of Arizona or the high rises of New York City, all sunsets have two things in common: light and atmosphere

It seems there may have been a typo in your question. It's possible you meant electromagnetic wave, which is a type of wave that consists of oscillating electric and magnetic fields. These waves can travel through a vacuum and are used for various purposes, such as communication and energy transfer.

Double refraction is when you can see through a mineral and it shows two images instead of one.

Calite is the mineral that exhibits it.

I linked a great website for this kind of stuff below.

sound waves are pressure waves that can push a thin membrane in a microphone. that membrane is attached to a magnet that moves through a loop of wires called a solenoid. the motion of a magnetic field moving through a solenoid generates an electric current (an electro-magnetic wave)

that signal can be transported down a wire and re-interpreted at another telephone.

The order of colors from longest to shortest wavelength is red, orange, yellow, green, blue, indigo, violet (ROYGBIV).

Gamma rays have the highest energy and are the most powerful waves on the electromagnetic spectrum.

Electromagnetic radiation can be dangerous at high levels of exposure, such as from nuclear radiation or prolonged exposure to high energy sources like X-rays. However, everyday exposure to low levels of electromagnetic radiation from sources like cell phones and Wi-Fi is generally considered safe.