General Science GK Questions with Answers – Page 107

A microphone is a transducer: sound waves strike a thin diaphragm, the diaphragm vibrates, and that mechanical vibration is turned into a varying electric signal.

At sunset the Sun is close to the horizon, so its light travels through a much thicker layer of atmosphere before it reaches the eye.

Green plants use sunlight trapped by chlorophyll to join carbon dioxide and water, and the balanced equation reads six molecules of carbon dioxide plus twelve of water giving one molecule of glucose, six of oxygen and six of water.

In an astronomical telescope set for normal adjustment, the magnifying power equals the focal length of the objective divided by the focal length of the eyepiece.

Heating a liquid makes its molecules move faster and sit a little further apart, so the attraction between them weakens, and both properties depend on that attraction.

Germanium is not used to build light emitting diodes because it is an indirect band gap semiconductor, so an electron falling back across the gap gives up most of its energy as heat in the crystal rather than as light.

This is the statement that is not correct, because water has a much higher surface tension than ethyl alcohol.

Villi are the small finger-like folds on the inner wall of the small intestine, so they belong to the digestive system.

The gastric glands in the stomach wall release three things: hydrochloric acid, the enzyme pepsin and mucus.

A solar cell turns sunlight straight into electricity by the photovoltaic effect at a semiconductor junction, usually of silicon, so nothing inside it turns or slides.

Hydrogen has three isotopes: protium with one proton and no neutron, deuterium with one proton and one neutron, and tritium with one proton and two neutrons.

A whale is a mammal, not a fish, so it breathes with lungs and must come to the surface to take air through a blowhole on top of its head.

It is a molecule of sixty carbon atoms arranged in a closed cage of pentagons and hexagons, exactly like the panels of a football, and it is named after the architect who designed domes of the same geometry.

Ethanoic acid, better known as acetic acid and familiar as vinegar in dilute form, has the formula CH3COOH, and the -COOH group at the end is what makes it acidic, since it releases a hydrogen ion in water and turns blue litmus red.

Vegetable oils contain unsaturated chains with carbon to carbon double bonds; hydrogen adds across those double bonds in the presence of nickel or palladium, turning them into single bonds, so the oil becomes saturated and sets into a solid fat.

Going from methane to ethane, or from ethanol to propanol, adds one carbon atom of mass twelve and two hydrogen atoms of mass one each, which is fourteen in all, and it is this fixed step that defines a homologous series.

In graphite every carbon atom is bonded to only three others within a layer, so the fourth valence electron of each atom is free to move along the layer, and moving electrons constitute an electric current.

Catenation is the self-linking of atoms of the same element, and carbon shows it more strongly than any other element because the carbon to carbon bond is short and exceptionally strong, which is why chains of many carbon atoms remain stable.

When enough air reaches the burner, every carbon atom of the fuel is oxidised fully to carbon dioxide and the flame is blue and hot, giving the maximum heat for the gas consumed.

An alkyne contains a carbon to carbon triple bond, which needs at least two carbon atoms, so the series begins with ethyne, C2H2, also called acetylene and used with oxygen in welding.