science & tech MCQ section 6 Practice Questions Answers Test with Solutions & More Shortcuts

Answer: (c)

We see colours because of the way light is reflected off of objects or substances. Light can either be absorbed into the object (or substance) or reflected.

If an object or substance absorbs all wavelengths (colours) except blue, blue will be reflected and that is the colour we see. If a substance absorbs all wavelengths except red and yellow the object will appear orange. If an object or substance absorbs no wavelengths but reflects them all, it is white - not black, as you might think. The colour white is a combination of all colours. Black is the absence of any colour.

Space is black because there are no substances or objects to reflect back any colour (or all colours, which would make it white). That is also why the astronauts see the earth as we see it in photos, but the space around it is black.

The light from the sun is reflected back as the blues and greens and browns that we see, but the space around the earth is just that - empty space and therefore does not reflect back any colours, so it is black.

Answer: (a)

A geosynchronous satellite is a satellite in geosynchronous orbit, with an orbital period the same as the Earth’s rotation period. Such a satellite returns to the same position in the sky after each sidereal day, and over the course of a day traces out a path in the sky that is typically some form of the analemma.

Geosynchronous satellites have the advantage of remaining permanently in the same area of the sky, as viewed from a particular location on Earth, and so permanently within view of a given ground station.

Geostationary satellites have the special property of remaining permanently fixed in exactly the same position in the sky, meaning that ground-based antennas do not need to track them but can remain fixed in one direction.

Answer: (d)

Compounds including Carbon dioxide, Nitrous oxide, Black carbon, Methane, Sulphur dioxide and CFCs are major contributors to global warming.

Answer: (b)

Heavy water, formally called deuterium oxide (D2O), is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium, (also known as heavy hydrogen). In nuclear reactors, heavy water acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238.

Answer: (d)

BrahMos is a supersonic cruise missile that is developed jointly by India’s DRDO and Russia’s NPO. The acrynonym of BrahMos is perceived as the confluence of the nations represented by two rivers, the Brahmputra of India and the Moskva of Russia.