We're on the Same Wavelength Trivia Quiz

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).

Answer: Voice telephony

The "V" in VF stands for "Voice" and the VF band is the spectrum used in traditional analog telephones which indeed do not transmit frequencies outside the 300 to 3,000 Hertz range well. Another name for this band is ULF (Ultra-Low Frequency); however, since practically no wireless applications for this frequency range exist, the VF designation is the most common.

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.

Answer: HF

When transmitted through the atmosphere, both MF and LF waves create so-called ground waves - they do not propagate in a straight line but actually follow the curvature of the earth due to the moisture present in the ground and seas actually bending the wave. HF and VHF waves both are unaffected by this phenomenon, but HF waves have the additional property of being relected quite well by the upper atmosphere (the ionosphere), thus "bouncing" around the globe. VHF and shorter waves do not show this reflection except under specific, uncommon atmospheric conditions and thus communication is usually limited to line of sight.

Answer: VHF only

The VHF band ranges from 30 to 300 Megahertz, but FM radio only uses the small region from 87.5 to 108 Megahertz (depending on jurisdiction, these numbers may be slightly different). Due to the fact that VHF transmitters and receivers are among the easiest to build, any bandwidth in this region is very valuable and many services, including all communication with airplanes, many emergency systems, and a small number of television channels use this band, but most television broadcasting occurs in the next higher UHF (Ultra-High Frequency) band.

Answer: Microwave ovens

The microwave oven actually uses a frequency (around 2.4 Gigahertz) that is still in the UHF band while all other applications use the frequency band of 3 to 300 Gigahertz. At these high frequencies, it usually becomes much easier to talk about them in terms of wavelengths, thus SHF and EHF represent waves of 10 centimeters down to 1 millimeter. Radar and wireless networks currently mostly operate in the 1 to 10 centimeter band, but plans exist for both to expand into the largely unused millimeter band.

The controversial touchless security scanners introduced at airports around 2010 also operate in the millimeter band.

Answer: It would cause burns

Infrared radiation (often inaccurately called thermal radiation or heat rays) are invisible to the human eye, but are easily felt due to their strong tendency to heat up any material they are absorbed by. Unlike microwaves, which specifically heat only water, infrared radiation is readily absorbed by almost any material and converted into heat. Strong infrared radiation can heat materials to several hundred and even thousand degrees centigrade within a fraction of a second and thus cause severe burns or ignite fires. Most immediate casualties from the nuclear attacks on Japan in World War II were actually due to this infrared radiation - bodies were burned or even vaporized by it.

It is by the way inaccurate to consider infrared waves themselves as heat - they have no temperature by themselves. Heat is generated when these waves are absorbed by materials; thus an infrared radiator can heat a solid several meters away without affecting the air in between.

Answer: Night vision

Short-wavelength UV light is used both to thoroughly disinfect water and other transparent liquids and gases and to create the lithography patterns used in microchip design. In forensic analysis, longer-wavelength UV is being used to excite fluorescence in bodily fluids left behind at a crime scene - UV detectors can easily make visible blood and saliva traces that would be impossible to detect via normal inspection. Night vision devices usually use the infrared spectrum.

Answer: It has less than 5% energy efficiency

Even with today's technology, it is impossible to directly create X-rays using a chip like in a laser or LED. Instead, a vacuum tube is used in which electrons are accelerated to extremely high speed and then colliding with other materials (typically metal atoms), dissipating their impact energy as a high-powered photon. Even in this reaction, however, less than one percent of the energy actually results in usable "hard" X-ray radiation (the longer wavelengths of so-called "soft" X-rays are filtered out as they are easily absorbed by tissues, thus only adding to the harmful radiation dose while contributing nothing to the image).

Answer: Gamma ray emission involves a nuclear reaction

The once hard wavelength boundary of 10 picometers distinguishing between X-rays and gamma rays has been replaced with a definition according to source: X-rays are the result of a process that does not involve a nuclear reaction while gamma rays are caused by a nuclear reaction, be it a decaying nucleus, a byproduct of a nuclear fusion or fission or any other such source. Powerful X-ray generators can today produce radiation in the traditional gamma band while some nuclear decays emit gamma rays that approach or even break the lower bound of the X-ray band. Gamma rays from normal radioactive decay can range down to 0.1 picometers of wavelength, while the shortest wavelengths measured from astronomical sources are actually still much shorter - all the way down to 1 attometer (one millionth of a picometer).