![]() ![]() The larger the area, the greater will be the transfer of heat. It is also found that the transfer of heat by radiation is also affected by the surface area of the body emitting or absorbing heat. It is found that A dull black surface is a good absorber of heat as its temperature rises rapidly.Ī polished surface is a poor absorber of heat as its temperature rises very slowly. For example, take two surfaces, one is dull black and the other is a silver polished surface with a candle at the middle of the surface. The rate at which various surfaces absorb heat also depends upon the nature of those surfaces. It is found that a black dull surface is a good emitter of heat. Hot water is filled in Leslie’s cube and is placed with one of its faces towards a radiation detector. ![]() The four faces of Leslie’s cube may be as follows: ![]() Emission and Absorption of Radiation:Ī Leslie cube is a metal box having faces of different natures. Various surfaces can be compared using Leslie’s cube. The rate at which various surfaces emit heat depends upon the nature of the surface. As a result, its temperature goes on increasing until it becomes equal to its surroundings. When the temperature of an object is lower than its surroundings, then it is radiating less heat than it is absorbing. At this stage, the body is giving out the amount of heat equal to the amount of heat it is absorbing. As a result, its temperature goes on decreasing until it becomes equal to its surroundings. When the temperature of an object is higher than its surroundings then it radiates more heat than it is absorbing. However, they are also absorbing heat at the same time. Why does a cup of hot tea become cold after sometime?Īll the objects, lying inside a room including the walls, roof, and floor of the room are radiating heat. The rate at which radiations are emitted depends upon various factors such as: A sheet of paper or cardboard kept in the path of radiation stops these waves to reach us. The heat from the fireplace reaches us directly by a different process in the form of waves called radiation. Heat does not reach us by convection because the air getting heat from the fireplace does not move in all directions. Heat does not reach us by conduction through the air from a fireplace because air is a poor conductor of heat. How does heat reach us directly from a fireplace? The emission of gamma rays by a nucleus.The light emitted by an incandescent lamp.Solar ultraviolet radiation is precisely the process that determines the Earth’s temperature.The transmission of electromagnetic waves through the microwave oven.Additionally, various technologies, such as radio communication and medical imaging, rely on different types of radiant energy, such as radio waves and X-rays, respectively. For instance, sunlight is a significant source of radiant energy, as it emits electromagnetic waves that include visible light. In everyday life, radiant energy is present in numerous forms. This property makes radiant energy a fundamental component in the field of lighting, as it is responsible for the emission and perception of light. Unlike potential energy, which is stored and can be used later, radiant energy is in constant motion and can be transmitted and absorbed by various materials. Radiant energy is characterized by its ability to transfer energy from one object to another. Radiant energy encompasses a broad spectrum of electromagnetic radiation, including solar energy, gamma rays, radio waves, X-rays, and visible light. It is a type of kinetic energy associated with the motion of electromagnetic waves. ![]() Radiant energy refers to the electromagnetic energy that is propagated through space in the form of transverse waves. ![]()
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