Electromagnetic Spectrum and Optics Trivia

1. The lowest named band of radio waves is ELF, standing for "extremely low frequency". Where would you most commonly encounter such an electromagnetic wave?

From Quiz We're on the Same Wavelength

Answer: In mains electricity

The ELF band encompasses the frequency from 3 to 300 Hertz (cycles per second). It is not a band used for significant radio transmission due to the need for extremely large transmitter and receiver antennas. However, normal household power - AC voltage cycled at 50 or 60 Hertz - falls into this band. ELF waves also occur in nature as a result of lightning strikes. Some sources subdivide the ELF band into two sub-bands, using ELF only for frequencies to 30 Hz and naming the 30 to 300 Hz band as SLF (Super Low Frequency).

From Quiz And Then There Was Light

Answer: 0.0000007 meters

One nanometer is one billionth of a meter, so 700 nm is six zeros after the decimal point before the seven.

From Quiz They Do It With Mirrors

Answer: Kaleidoscope

The word kaleidoscope comes from Greek words which translate literally as 'observer of beautiful shapes'. Sir David Brewster invented the device in 1816, during research into polarized light, and expected it to be a serious scientific tool, but it was quickly turned into a children's toy. The long main tube contains several mirrors along its length, set at angles to produce multiple reflections of the objects; the pattern depends on the number of mirrors used and the angle between them. As the tube is rotated, the loose colored objects fall into different positions, producing an ever-changing pattern. Some kaleidoscopes simply have mirrors, producing a pattern based on reflections of the external environment.

From Quiz Electrifying Physics!

Answer: Coulombs

The coulomb is named after Charles-Augustin de Coulomb. The charge of an electron is -1.6 x 10 to the power -19 coulombs. You can therefore calculate the number of electrons which have flowed past a particular point by dividing the total charge by the charge of one electron.

From Quiz Light My Way

Answer: He published a book about how light travels.

The book was called 'Astronomiae pars Optica'. He explained that light travels in straight lines, how it cast shadows, and that it would bend when moved from one substance to another. He is also the person that discovered why near and far sighted people had blurred vision. Sidenotes: The hologram wasn't outlined until the 1900's. The lacemaker's condenser was an invention that used a candle surrounded by globes of water to concentrate light beams for detail work.

From Quiz Light

Answer: One ray of white light

Since the ray of white light strikes the glass surface normally and the angle of incidence will be zero, there will be no refraction of light and as a result, no separation of white light into its constituent rays.

From Quiz The Colours of Optics

Answer: Cyan, magenta, and yellow

The additive colours are red, blue, and green.

From Quiz And Then There Was Light

Answer: optics

In addition to interaction with light, optics includes instrumentation used to detect it. Optics are used to study very small features such as atoms and very large objects such as galaxies. Originally optics for both purposes were made of glass.

From Quiz Electrifying Physics!

Answer: Current x voltage x time

No matter how you calculate energy, all can be expressed in joules. Electrical power can be found by current x voltage, as a watt is a joule per second.

From Quiz The Science of Color

Answer: psychophysical

Color is the perception or subjective response of an individual observer to the physical stimulus of visible light. Color, therefore, has both a subjective and objective component and does not have a direct correspondence with spectral energy.

From Quiz Light My Way

Answer: It is the middle of a shadow during solar eclipse.

In the umbra, all of the sun's light is blocked. If you are in the path of the umbra, you will experience a total eclipse. The edges of the shadow are called penumbra. In the path of penumbra, only a partial eclipse will be experienced.

From Quiz The Colours of Optics

Answer: Red, green, blue

Mixing two additive colours gives you a subtractive colour. Red and blue make magenta, green and blue make cyan, and red and green make yellow.

From Quiz We're on the Same Wavelength

Answer: A submerged submarine

Waves shorter than the VLF range cannot penetrate water while waves longer than it are not only extremely hard to produce in significant strength but also cannot carry any significant data rate. Even VLF radio has too narrow a bandwidth to support a clearly modulated voice signal, so transmission is limited to low-bit-rate digital data such as navigational information. VLF signals can be received up to approximately 40 meters below the surface - deep enough for most submarine operations.

From Quiz And Then There Was Light

Answer: refraction

Refraction makes it appear that an object is bent because the speed of light is different in two materials with different indices of refraction.

From Quiz Light My Way

Answer: A dependable way of predicting how far light will bend.

There were other theories before Snell's, but his was the first that was truly reliable. He created a ratio that had to do with the angles of the light beams entering a substance. He also realized different substances would bend light different amounts. He created the refractive index to cover this. Sidenotes: E=mc2 is Einstein's Equivalence of Energy and Matter. 'For every action' is Newton's third law of Physics. Newton and Cassegrain designed some of the first reflecting telescopes.

From Quiz And Then There Was Light

Answer: TV and radio waves

TV and radio waves are on the long end of the EM spectrum. They can be meters long. Since wavelength is inversely proportional to energy, these are the lowest energy waves. On the other end of the spectrum are x-rays and gamma rays, which have short wavelength and high energy.

From Quiz Maxwell's Equations

Answer: It's proportional to the charge inside

These are really just two equivalent ways of stating Gauss's law. Start with the differential form of the law: the divergence of the electric field E is equal to the charge density, rho, times a constant. Now let's integrate both sides over some volume. (Integration is a mathematical method for adding up all the values of an expression in some region, in this case a volume of space.) A charge density has units of charge per volume, so when you integrate it over a volume, you end up with the total charge. Meanwhile, there's a theorem of calculus that tells us how to integrate the divergence of E over a volume: it's the same as integrating E over the surface that encloses the volume, and we know that's the definition of the flux. So, there we have it: the flux of the electric field through a closed surface (that is, a surface that goes all the way around a volume) is equal to the charge inside, times a constant. What's the constant? This depends on what units you're using and what material you're studying. In a vacuum and in SI units, which include such favorites as meters, Volts, and Amperes, the constant of proportionality here is one divided by epsilon0, the permittivity of free space. This has been measured to be 8.85 million-millionths Coulomb-squared per Newton per meter-squared.

From Quiz The Science of Color

Answer: temperature

Color temperature is the temperature (in Kelvin) at which a black body radiator will match the light source, and is related to Planck's Law. Note that all light sources are illuminants, but not all illuminants are light sources, since illuminants can be theoretical or use mixed light sources.

From Quiz Light My Way

Answer: A shadow cast on a cloud and surrounded by colored rings.

This phenomenon occurs high in the mountains. When the conditions are right and someone climbs higher than the sun's position, then this trick of light might be witnessed. It is named for the German mountain, Brocken.

From Quiz Light

Answer: Convex lens

Convex lenses converge light only when placed in a medium less dense than the material they are made of, otherwise they diverge light. The reverse happens with concave lenses. This is why it is inappropriate to designate lenses as 'converging' or 'diverging', as this property is subject to change. Note: Water is denser than ice. Both are transparent.

From Quiz And Then There Was Light

Answer: x-rays

X-rays are waves that are energetic enough to pass through the human body, but are less harmful than gamma rays. Microwaves and ultrasound have longer wavelengths and thus are less energetic.

From Quiz Electrifying Physics!

Answer: Kirchhoff's 1st law

This is because in a series circuit there is only one "route" the current can take and so it is not divided. Kirchhoff's 2nd law states that the potential difference supplied to a circuit is equal to the sum of the potential differences across the individual components of the circuit.

From Quiz Maxwell's Equations

Answer: Magnetic charges (i.e. monopoles) do not exist.

A magnetic monopole would be a net magnetic charge, similar to an electric charge -- but magnets don't seem to work that way. A permanent magnet always has a north pole and a south pole: no net magnetic charge. Electromagnets work the same way. Yet, if magnetic monopoles existed, they might illuminate a great deal -- for example, Paul Dirac showed that their existence would explain why electric charges come in discrete units, or quanta. String theory, and attempts at Grand Unified Theories (combinations of electromagnetic, weak and strong forces), all require monopoles -- so, of all four of Maxwell's equations, this is the one that inspires substantial experimental effort to disprove it. Some experiments use sensitive magnets to look for natural monopoles; others look for evidence that they are being created in high-energy collisions in particle accelerators. Perhaps there will be exciting monopole news in the next few years!

From Quiz The Science of Color

Answer: metamerism

Metamerism can be predicted. When the reflectance spectra of two objects cross three or more times, the objects are metamers. Unfortunately, it is not easy to predict exactly under which illuminants the two objects will match or not.

From Quiz Light My Way

Answer: a mixture of many other light colors

The three primaries of light are red, blue, and green. When the primary colors of light are combined equally, white light is the result. Newton wrote all about light in his book, 'Opticks'. He experimented splitting white light into spectrums using prisms.

From Quiz Light

Answer: 1 : 1

All colours of light have the same speed in air and vacuum.

From Quiz The Colours of Optics

Answer: White

This is because magenta is a subtractive colour made up of red and blue. When added with green, this is like mixing all three additive colours together, which would make white light.

From Quiz And Then There Was Light

Answer: Excitation of water molecules

The microwaves have just the right energy to causes stretching of the bonds in water molecules. This stretching and the resulting relaxation releases energy in the form of heat.

From Quiz They Do It With Mirrors

Answer: Concave parabolic

When light is emitted from a globe placed at the focal point of a concave parabolic mirror, the reflected light is directed parallel to the parabola's axis of symmetry. Concave parabolic mirrors are also used to reflect parallel light rays from a distant source so that they all meet at the focal point, producing an increased intensity. The familiar shape of a satellite dish is a concave parabola. Concave surfaces, curved so that the light approaches a surface whose sides are curving towards it, cause the light from a distant source to focus. Spherical mirrors do not produce a single focal point, a fact which is described as spherical aberration. Parabolas produce a far superior focal point. Convex surfaces, curved so that the light approaches a surface whose sides are curving away from it, cause the light to be spread out. Plane, or flat, surfaces change the direction of the reflected light uniformly.

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Last Updated Nov 16 2024 5:49 AM

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