ANSWER THESE QUESTIONS -:
1. Explain the working of LED.
2. How can we reduce, recycle and reuse water?
3. Plastics are replacing metals in the car industry. Give two possible reasons to
support your answer.
4. Amit wishes to buy a shirt. The shopkeeper shows him one shirt each of cotton
and rayon. He decides to buy the cotton shirt. What are the two properties of cotton
shirt that it prefers over rayon.
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Answer:
1) Working Principle: A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons.
2) Reuse Water From Old Drinking Bottles, Use a Rain Barrel to Save Runoff, From Your Roof, Water the Plants With Pasta Water, Reuse the Water You Washed Your Veggies With, Place a Bucket in the Shower, Install a Grey Water Collection System.
3) In the car industry plastic is replacing metals because plastics are cheaper than metals and plastics can be easily molded in various shapes.
4) Cotton fibers are natural hollow fibers; they are soft, cool, known as breathable fibers, and absorbent. Cotton fibers can hold water 24–27 times their own weight. They are strong, dye absorbent, and can stand up against abrasion wear and high temperature. In one word, cotton is comfortable.
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⇒ Question - Explain the working of LED
⇒ A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light (corresponding to the energy of the photon) is determined by the energy band gap of the semiconductor.
Working in a nutshell:
➡️The material used in LEDs is basically aluminum-gallium-arsenide (AlGaAs). In its original state, the atoms of this material are strongly bonded. Without free electrons, conduction of electricity becomes impossible here.
By adding an impurity, which is known as doping, extra atoms are introduced, effectively disturbing the balance of the material.
➡️These impurities in the form of additional atoms are able either to provide free electrons (N-type) into the system or suck out some of the already existing electrons from the atoms (P-Type) creating “holes” in the atomic orbits. In both ways the material is rendered more conductive. Thus in the influence of an electric current in N-type of material, the electrons are able to travel from anode (positive) to the cathode (negative) and vice versa in the P-type of material. Due to the virtue of the semiconductor property, current will never travel in opposite directions in the respective cases.
➡️ the intensity of light emitted from a source (LED in this case) will depend on the energy level of the emitted photons which in turn will depend on the energy released by the electrons jumping in between the atomic orbits of the semiconductor material.
➡️We know that to make an electron shoot from lower orbital to higher orbital its energy level is required to be lifted. Conversely, if the electrons are made to fall from the higher to the lower orbitals, logically energy should be released in the process.
➡️In LEDs, the above phenomena is well exploited. In response to the P-type of doping, electrons in LEDs move by falling from the higher orbitals to the lower ones releasing energy in the form of photons i.e. light. The farther these orbitals are apart from each other, the greater the intensity of the emitted light.
➡️Different wavelengths involved in the process determine the different colors produced from the LEDs. Hence, light emitted by the device depends on the type of semiconductor material used.
Infrared light is produced by using Gallium Arsenide (GaAs) as a semiconductor. ➡️Red or yellow light is produced by using Gallium-Arsenide-Phosphorus (GaAsP) as a semiconductor. Red or green light is produced by using Gallium-Phosphorus (GaP) as a semiconductor.
⇒ Question - How can we reduce, recycle and reuse water?
⇒ A few ways to save water are :-
➡️Place a Bucket in the Shower.
➡️Reuse Water From Old Drinking Bottles.
➡️Use a Rain Barrel to Save Runoff From Your Roof.
➡️Water the Plants With Pasta Water.
➡️Reuse the Water You Washed Your Veggies With.
➡️Install a Grey Water Collection System.
⇒ Question - Plastics are replacing metals in the car industry. Give two possible reasons to support your answer.
⇒
➡️ Weight: the plastic is about six times lighter than the zinc, less weight means better gas mileage (which the car companies are under federal law to improve)
➡️ Cheaper: When the plastic doesn't have to get painted (for trim parts), it is extremely cheaper (50%+).
⇒ Question - Amit wishes to buy a shirt. The shopkeeper shows him one shirt each of cotton and rayon. He decides to buy the cotton shirt. What are the two properties of cotton shirt that it prefers over rayon.
⇒ Cotton fibers are natural hollow fibers; they are soft, cool, known as breathable fibers and absorbent. Cotton fibers can hold water 24–27 times their own weight. They are strong, dye absorbent and can stand up against abrasion wear and high temperature. In one word, cotton is comfortable. Since cotton wrinkles, mixing it with polyester or applying some permanent finish gives the proper properties to cotton garments. Cotton fibers are often blended with other fibers such as nylon, linen, wool, and polyester, to achieve the best properties of each fiber.
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