Infrared
0Loading crowd target
0Loading crowd target
7correct to beat the crowd
40 free Infrared trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Infrared is the light we feel instead of see. It sits just outside the red edge of the rainbow, pours out of every warm object, and was stumbled upon more than two centuries ago by someone who was only trying to measure the warmth of colours. This quiz collects the fun facts people look for about infrared waves: how the invisible radiation was found and named, which animals can sense it, why astronomers prize it, and how it slipped into living rooms, hospitals, rescue kit and games consoles. It suits curious players, science students and anyone revising the electromagnetic spectrum. Every question comes with a short explanation, so you come away with a fact worth repeating.
30 of 40 questions with answers and explanations. Play the quiz
Q 01Which mammal uses infrared-sensitive receptors on its nose to home in on its prey's body heat?
Vampire bat
The vampire bat has heat receptors on its nose-leaf that are thought to guide it to where blood flows closest to the skin. It is the only mammal known to feed entirely on blood.
Q 02The infrared flash from a TV remote, invisible to the naked eye, shows up on the screen of which gadget?
A smartphone
A smartphone shows the flash because its camera registers the coded flashes of light that human eyes cannot see. Each button press on the remote sends out a fresh stream of them.
Q 03Infrared scans found a hidden portrait of a bearded man beneath The Blue Room, painted by which artist?
Pablo Picasso
Pablo Picasso painted The Blue Room in 1901 as a struggling 19-year-old in Paris who could not afford a new canvas for every idea, so he reused old ones.
Q 04Which Nintendo console's Sensor Bar is really a row of infrared LEDs that the handheld controller tracks?
Wii
The Wii puts five infrared LEDs at each end of its Sensor Bar, and an image sensor inside the remote watches those points of light to work out where it is aimed.
Q 05Infrared night-vision goggles show an image in which single colour, judged easiest to view for long periods?
Green
Green was chosen because it was considered the easiest colour to look at for long spells in the dark. The goggles turn faint light into electrons, amplify them, then turn them back into a visible image.
Q 06The jewel beetle Melanophila acuminata uses infrared-sensing organs to find what, where it lays its eggs?
Forest fires
Forest fires draw the beetles in huge swarms to lay eggs in freshly burnt wood, and adults keep returning to the charred timber for up to a year.
Q 07Which NASA space telescope, launched on Christmas Day 2021, studies the early universe in infrared?
James Webb
James Webb works in infrared because light from the earliest galaxies has been stretched out of the visible range on its long journey. A five-layer sunshield keeps the telescope cold.
Q 08Firefighters carry thermal imaging cameras because infrared lets them see people and hot spots through what?
Smoke
Smoke hides flames and people from the eye, but a thermal camera turns their heat into a visible picture, letting crews find victims and the seat of a blaze quickly.
Q 09Which German-born British astronomer discovered infrared in 1800 by splitting sunlight with a prism?
William Herschel
William Herschel found that warmth kept increasing past the red end of the spectrum, where no light could be seen. He had first come to Britain from Hanover as a musician.
Q 10Which device, placed just past the red end of a prism's spectrum, revealed infrared with a rising reading?
A thermometer
A thermometer placed just outside the red light showed a rise in temperature, revealing rays nobody could see. The experiment had set out to measure the heat of each colour.
Q 11What does the Latin prefix infra mean in infrared, describing where the rays sit relative to red light?
Below
Below is the meaning: the rays sit just under red light in frequency and energy. Infrasound, sound pitched too low to hear, borrows the same prefix.
Q 12Rattlesnakes strike warm prey in total darkness using infrared organs that give which snake group its name?
Pit vipers
Pit vipers are named for the heat-sensing hollow between each eye and nostril. In experiments, blindfolded rattlesnakes have still struck their prey accurately.
Q 13Infrared lasers carry long-distance internet and phone signals through which kind of cable?
Fiber-optic
Fiber-optic lines use infrared because it travels along the strands with far less loss than electricity in a metal wire, so signals can run long distances between boosts.
Q 21NASA's SOFIA observatory flew an infrared telescope into the stratosphere aboard which modified airliner?
Boeing 747
A Boeing 747 of the shortened SP type, with a large door cut into its fuselage, flew the telescope about 12 kilometres up. The retired jet is now on show at a museum in Arizona.
Q 22Infrared telescopes can watch stars being born because infrared passes through which material in space?
Dust
Dust soaks up visible starlight but lets longer infrared waves through, opening a view into star-forming regions and the crowded centres of galaxies.
Q 23Infrared telescopes are flown on aircraft or built on high peaks to get above which absorbing gas?
Water vapor
Q 14Which Apple feature works in the dark by projecting more than 30,000 invisible infrared dots onto its user?
Face ID
Face ID reads the dot pattern with an infrared camera to build a 3D map of the face. The depth-sensing technology grew out of a body-tracking sensor made for a games console.
Q 15Which medical device clips onto a fingertip and shines red and infrared light through it?
Pulse oximeter
A pulse oximeter compares how much of each light gets through, because oxygen-rich blood absorbs more infrared while oxygen-poor blood absorbs more red.
Q 16Which burglar-alarm devices, often labelled PIR, are triggered by a person's infrared body heat?
Motion detectors
Motion detectors of this kind send out nothing themselves, which is what the P for passive means. They react to the jump from room temperature to body temperature as someone crosses their view.
Q 17Every object gives off infrared or other thermal radiation unless cooled to which theoretical temperature?
Absolute zero
Absolute zero, about minus 273 degrees Celsius, is the only temperature at which matter would stop radiating, so even an ice cube glows in infrared.
Q 18On the electromagnetic spectrum, infrared sits between visible red light and which lower-frequency band?
Microwaves
Microwaves come next as wavelengths lengthen, followed by radio waves. The far edge of infrared blurs into them in the terahertz region, which can be counted as part of either band.
Q 19Infrared weather-satellite images let forecasters track the height and type of what throughout the night?
Clouds
Clouds show up after dark because infrared images map temperature instead of reflected sunlight. High, cold tops such as thunderheads stand out from lower, warmer layers.
Q 20NASA's largest infrared space telescope has mirrors coated in which metal for its infrared reflectivity?
Gold
Gold coats all 18 hexagonal beryllium segments, which together form a mirror 6.5 metres across, far wider than the one on Hubble.
Water vapor absorbs much of the infrared arriving from space, so astronomers go to high altitudes, or lift telescopes on balloons, to climb above most of it.
Q 24The IRAS infrared space telescope stopped observing after ten months when it ran out of which coolant?
Liquid helium
Liquid helium kept the telescope at about minus 271 degrees Celsius so its own warmth would not drown out faint signals. All 73 kilograms had boiled away by November 1983.
Q 25Which US heat-seeking missile is named after a desert rattlesnake that itself hunts by sensing infrared?
Sidewinder
Sidewinder was picked in 1950 as the name of the AIM-9, an air-to-air missile; the snake it honours finds warm-blooded prey with heat-sensing organs of its own.
Q 26Edme Mariotte showed in 1681 that which material, though clear to sunlight, blocks invisible radiant heat?
Glass
Glass of the ordinary window kind is opaque to long-wave infrared, which is why a thermal camera cannot see through a window pane.
Q 27Thermal camera lenses are often cut from which grey element, opaque to the eye but clear to infrared?
Germanium
Germanium looks like dull metal yet lets infrared pass, so it can be cut and polished into lenses and windows. Decades earlier, it was the material that launched the transistor age.
Q 28Samuel Langley's 1880 bolometer could sense the infrared warmth of which farm animal a quarter mile away?
A cow
A cow standing 400 metres off was enough to register on the device, which measured tiny temperature changes in thin metal strips blackened with lampblack.
Q 29After the discovery of infrared, Johann Ritter searched the spectrum's other end and found what in 1801?
Ultraviolet
Ultraviolet turned up when Ritter, hunting for cooling rays to match the heat rays, saw paper soaked in silver chloride darken fastest just outside the visible colours.
Q 30In near-infrared landscape photographs, what turns as bright white as snow, giving a dreamlike look?
Tree leaves
Tree leaves and grass reflect near-infrared the way snow reflects visible light. Photographers name the look after Robert W. Wood, who published early infrared photographs in 1910.