Which one of the following is not an example of convection? An eagle soars on an updraft of wind. A person gets a suntan on a beach. An electric heater warms a room. Smoke rises above a fire. Spaghetti is cooked in water.

The statement that is not an example of convection is (A person gets a suntan on a beach).

Explanation:

There are different modes of heat energy transfer which includes:

--> conduction

--> Radiation and

--> Convection

CONVECTION is a process by which heat energy is transferred in a fluid or air by the actual movement of the heated molecules. The cooler portion of the air surrounding a warmer part exerts a buoyant force on it. As the warmer part of the air moves, it is replaced by cooler air that is subsequently warmed.

Convection in gases is very common and gas expands more than liquid when subjected to high temperature.

--> it is used in bringing about the circulation of fresh air in the room in a process known as ventilation.Here, cool air is constantly being replaced with denser air ( warm air).

-->An electric heater warms a room and Smoke rises above a fire are typical example of convection in gases.

-->Spaghetti is cooked in water: As the water close to the burner warms, it rises to the top and boils. At the same time, cooler water on top moves downward to replace the rising hot water.

--> also the eagle uses convection current to stay afloat in the sky without flapping its wings to conserve energy.

But the option (A person gets a suntan on a beach) is an example of heat transfer through radiation. This is because the sun emits it's rays from the sky down to earth without any material medium unlike others. Therefore, this option is the ODD one out.

The half-life of this radioactive isotope is 9 months for it decreases to one-fourth its original amount in 18 months. Half-life means a certain length of time after which half of the amount of radioactive element has decayed.
Therefore, the half-life of this particular isotope is 18 months. After 18 months the isotope was at one-half, then another 18 months, the isotope was at one-fourth, which is 9 months where one-fourth is one-half of one half.