# Types of Heat Transfer: Radiation

#### Academic Questions in PhysicsPlease click here to see all Questions and Answers Which of the following is a fundamental quantity? A. Luminous Intensity B. Area C. Volume D. Velocity E. Concentration F. Acceleration An object at rest will temporarily stay in its state of rest, and if the object is in uniform motion, it will temporarily move in a straight line, unless an external force acts upon it. The above statement refers to Sir Isaac Newton's first law of motion. A. True B. False Which of the following statement is incorrect concerning gravity? A. The force of gravity is generally considered the strongest force among the four forces that govern the universe B. Your weight changes as you travel away from the earth C. If we dig the earth until we get into its center, we will have no weight as a result of lack of gravity D. Gravity prevents us from falling off the constantly rotating earth E. If a hammer and a feather are dropped simultaneously in a vacuum, they will both land at the exact same time as a result of gravity F. Weight is always a function of gravity Sir Isaac Newton was hit by an apple when he pondered on force, motion and gravity. A. True B. False The movement of gaseous particles through a tiny hole is termed _____. A. Osmosis B. Diffusion C. Effusion D. Infusion E. Defusion F. Gaslusion A lighted bulb transfers heat through a process termed _____. A. Conduction B. Convection C. Radiation D. Oxidation E. Reduction F. Electrical Induction A measurement of how much the velocity of an object changes with time is termed _____. A. Displacement B. Acceleration C. Speed D. Momentum E. Velocity-Time graph F. Average velocity Which of the following differentiates velocity from speed? A. Distance B. Time C. Momentum D. Inertia E. Direction F. Distance and Time

The term 'radiate' in English means to spread out from a central point. For instance, the light from the sun radiates to the earth. Also, a lighted bulb will radiate its light in a dark room.

The term radiation (heat radiation) can simply be defined as the transfer of heat in the form of electromagnetic waves.

Whenever heat is transferred via radiation, a contact surface will not be required between the heat source and the object being heated. In this case, the heat is transmitted through space.

One reason why some people put out their bulbs before they go out is to simply conserve energy. Leaving on the bulb will bring an extra heat into the room where it’s present.

Consider the points below regarding radiation through a lighted bulb:

• A bulb will possess a large amount of heat energy if left switched on for a long period of time. Meanwhile, recall that a bulb converts electrical energy to light and heat energy.
• Since energy cannot be lost, the heat energy from the bulb will be radiated around the room where it’s present. The energy transfer goes thus:
###### Electrical Energy >> Light Energy >> Heat Energy

This process of heat transfer from the bulb to the room is a concept of radiation.

In radiation, the heat energy is transferred by electromagnetic waves. In fact, the heat energy which the earth receives from the sun is as a result of electromagnetic waves travelling through space.

The image below shows how heat is radiated to earth from the sun's solar energy: Electronic objects, for example: televisions, phones, computer and cars will always radiate energy in the form of electromagnetic waves. The rate at which this energy is released is directly proportional to the Kelvin temperature (T) raised to the fourth power.

The hotter an object is, the more its ability to radiate heat energy. The radiated energy is a collection of a range of wavelength referred to as emission spectrum.

The wavelengths within the spectra of the emitted radiation will decrease when the temperature of an object increases; and as a result, hotter objects will usually emit a shorter wavelength at a higher frequency. 