scientist, discoveries & inventions MCQ section 4 Practice Questions Answers Test with Solutions & More Shortcuts

Answer: (c)

Answer: (d)

The electron microscope was invented by Max Knoll and Ernst Ruska in 1931 (Germany). An electron microscope uses condensing lenses to focus a beam of electrons to illuminate a specimen and produce a magnified image.

An electron microscope (EM) has greater resolving power than a light-powered optical microscope because electrons have wavelengths about 100,000 times shorter than visible light photons.

The electron microscope uses electrostatic and electromagnetic “lenses” to control the electron beam and focus it to form an image.

These lenses are analogous to but different from the glass lenses of an optical microscope that forms a magnified image by focusing light on or through the specimen.

Answer: (c)

Answer: (c)

There are two ways in which scientists quantify the size of earthquakes: magnitude and intensity.

Magnitude measures the energy released at the source of the earthquake; Intensity measures the strength of shaking produced by the earthquake at a certain location. The Richter Scale is used for measuring the magnitude of earthquakes.

The magnitude value is proportional to the logarithm of the amplitude of the strongest wave during an earthquake. The mercalli scale is used to measure the intensity of earthquakes. The intensity of a quake differs greatly from place to place.

It depends upon such factors as the distance from the epicentre, the design and quality of construction of local buildings, and the type of surface beneath the buildings.

Answer: (b)

Gunpowder was the first chemical explosive and the only one known until the invention of nitrocellulose, nitroglycerin, smokeless powder, and TNT in the second half of the 19th century.

Prior to the invention of gunpowder, many incendiary and burning devices had been used, including Greek fire. Roger Bacon invented gunpowder.