Incandescent bulbs produce light by heating a filament to a very high temperature. The type of radiation emitted by a hot object depends on its temperature, as described by Planck's law and Wien's displacement law. We need to determine which part of the electromagnetic spectrum is predominantly emitted by a typical incandescent bulb.
Correct Option: C) Infrared radiation is the primary type of radiation emitted by incandescent bulbs. This is because their operating temperature causes the peak of their emission spectrum to fall in the infrared region, making them very inefficient at producing visible light (most energy is wasted as heat).
The question asks to identify the most energy-efficient lighting type among the given options. Energy efficiency in lighting refers to how much light (lumens) is produced per unit of electricity consumed (watts). We will compare the efficiency of each lighting technology.
Correct Option: D) LED lighting is considered the most energy-efficient type of lighting. They convert a much higher percentage of electrical energy into visible light compared to other technologies, resulting in lower energy consumption and longer lifespan.
The question asks to identify what 'lumens' measure. This requires knowledge of basic photometric units used in lighting and optics.
Correct Option: B) Luminous flux. Lumens are the SI unit for luminous flux, which quantifies the total amount of visible light emitted by a source.
The question asks about the primary function of the phosphor coating in fluorescent lamps. To answer this, one needs to understand the basic working principle of a fluorescent lamp.
C) To convert UV light to visible light — This is the core function of the phosphor coating in a fluorescent lamp. Without it, the lamp would primarily emit invisible UV radiation.
The question asks about the average lifespan of an LED bulb. This is a factual recall question related to common knowledge about lighting technology. We need to identify the typical operating hours for LED bulbs, which are known for their longevity compared to traditional lighting.
Correct Option: C) 25,000 to 50,000 hours. This range accurately reflects the typical average lifespan of commercially available LED bulbs, making them a highly energy-efficient and long-lasting lighting solution.
The question asks about the type of light emitted by a blackbody at high temperatures. We need to recall the characteristics of blackbody radiation and how it changes with temperature.
B) Continuous spectrum — A blackbody emits radiation across a continuous range of wavelengths. As its temperature increases, the intensity of all emitted wavelengths increases, and the peak of the emission spectrum shifts towards shorter wavelengths (higher frequencies), encompassing infrared, visible, and ultraviolet light, but always as a continuous distribution.