science & technology Online Quiz - 477

Antarctica's ice preserves meteorites against the white background, while desert regions like North Africa's Sahara also concentrate meteorites due to low erosion rates and high contrast. These two locations account for the majority of meteorite discoveries globally.

Chlorine gas appears greenish-yellow, a distinctive property that makes it visually identifiable among common gases. Hydrogen, krypton, and neon are all colorless gases under standard conditions.

Pencil 'lead' is actually graphite, a form of carbon, not the metal lead. The misnomer dates back to when graphite was mistaken for a lead ore. Graphite's layered structure allows smooth marking on paper.

In the visible spectrum, blue light has shorter wavelengths (450-495 nm) compared to green, yellow, and red. Violet actually has the shortest (400 nm), but among the given options, blue is correctly the shortest.

Lasers produce coherent, monochromatic light that can be focused to extremely small spot sizes, enabling the high-resolution printing required for sharp text and images. The claim that lasers are 'impossible to damage' is incorrect, making option D invalid.

'cw' stands for continuous wave, indicating the laser operates continuously rather than in pulses. Pulsed lasers emit energy in bursts, while continuous-wave lasers maintain steady output for applications like cutting, welding, or communication.

To determine the active medium used in the first working laser ever constructed, we need to understand the concept of an active medium in a laser.

The active medium in a laser is the material that provides the energy necessary to create laser light. It is typically a solid, liquid, or gas that can be excited to produce a population inversion, which is the condition required for stimulated emission of photons.

Now, let's examine each option:

A. A diamond block: While diamond is a material that can be used as an active medium in certain types of lasers, it was not used in the first working laser ever constructed.

B. Carbon dioxide gas: Carbon dioxide gas was not used in the first working laser ever constructed.

C. Helium-neon gas: Helium-neon gas is commonly used in helium-neon lasers, but it was not used in the first working laser ever constructed.

D. A ruby rod: The correct answer is D. The first working laser ever constructed, known as the ruby laser, used a ruby rod as its active medium. The ruby rod was excited using a flashlamp, which created a population inversion and allowed for the production of laser light.

Therefore, the correct option is D. A ruby rod was the active medium used in the first working laser ever constructed.

The first commercially successful oil well was drilled in Titusville, Pennsylvania, USA in 1859 by Edwin Drake. This marked the birth of the modern petroleum industry. The other countries listed became major oil producers much later.

Retinol is a form of vitamin A that is readily used by the body. It is considered one of the most active and bioavailable forms of vitamin A. Vitamin D, B, and K are completely different vitamins with distinct functions.

The King Cobra's scientific binomial name is Ophiophagus hannah, which literally means 'snake-eater' in Greek. Naja naja refers to the Indian cobra, a different species.

Fruit flies were the first animals sent to space aboard a U.S. V-2 rocket in 1947. They were chosen because they are small, reproduce quickly, and are biologically similar to humans in many ways. Laika (a dog) followed in 1957.