General Science Previous Year Questions (PYQ) with Answers – Page 8

Each of them is made of two simple sugar units joined together, which is exactly what a disaccharide is. Carbohydrates are grouped by the number of sugar units they contain.

Light slows down when it enters water from air, so a ray that strikes the surface at an angle bends towards the normal.

Villi are tiny finger-like folds of the inner lining of the small intestine that greatly increase its surface for absorbing digested food.

The ABO system sorts blood by the antigens present on the surface of red blood cells, and it has exactly these four groups.

Seen from the east end, the current flows away from the observer, and by the right-hand thumb rule the field lines around it are clockwise circles in a plane perpendicular to the wire.

Light travels fastest in a vacuum; in any material medium, including carbon disulphide, it slows down, so its speed there (X) is less than its speed in vacuum (Y).

A system whose walls let no heat pass in or out is called adiabatic, so any change in its state happens with zero heat exchange (Q = 0).

H₂S is a colourless gas with the familiar smell of rotten eggs, and the human nose can detect it even in very small amounts.

Nitrogen gas is the element itself in a very stable form, and plants cannot take it up directly from the soil or the air, so it is not used as a fertilizer.

Strain is a ratio of two lengths (or two volumes), so its units cancel and it has no dimensions. When a force deforms a body, strain measures the fractional change in its shape or size.

Resistivity is a property of the material itself, so changing the length of a copper wire does not change it.

. A simple astronomical (refracting) telescope uses two convex, that is convergent, lenses.

. For a stone whirled in a circle, the string pulls it towards the centre, while the stone moves along the circle, tangent to it at every instant.

By Archimedes' principle, the upward force, called buoyancy or upthrust, equals the weight of the fluid displaced by the body.

Tiny gas molecules in the air scatter short wavelengths far more strongly than long ones. This is Rayleigh scattering: the amount of scattering varies inversely with the fourth power of the wavelength.

Linear momentum stays constant only when no net external force acts. Linear momentum is the product of mass and velocity, p = mv.

This goes against the conservation of charge: the total charge of an isolated system always stays the same. Electric charge has three basic properties.

These two organelles carry their own circular DNA and their own small (70S) ribosomes, so they can make some of their own proteins.

The time period of a simple pendulum depends on the square root of its length and not on its mass, so four times the length gives twice the period.

Antibodies are made by B lymphocytes, which turn into plasma cells that release antibodies in very large numbers during an immune response.