Have a look at this Gold ring kept in front of you. Observe the shape of the ring. Wht do you observe? You can clearly see that the ring is somewhat deformed. When it was purchased, it used to be a perfect circle. How did it get deformed then? To change the shape of an object one needs to apply some force. What force was applied to the ring? In performance of our daily chores, like washing clothes, utensils, during exercises, playing sports, inadvertently lots of pressues are applied to the ring and this led to the deformation in shape of the ring. You must have packets of medicine at your home. Some of the medicines get expired before they can be used. Take a packet of a medicine that has got expired. These are made of Aluminium. Remove the tablets and keep the foil with you. Now roll these foils into a ball. Observe how easily it gets rolled into the shape of a ball without applying much pressure. Now take a hammer and hit this ball. Observe carefully, What happens to the ball? It becomes flat again. Keep hammering it and gets flatter and thinner. Now take a broken plastic container. Use hammer to deform its shape just like we had done with the packet of medicine. Observe what happens?
You will find that the plastic container instead of deforming, simply breaks down into pieces. Why different types of materials react differently to application of forces over them. On one hand we have the Plastic material which simply breaks on hammering. On the other extremes we have the Aluminium foil and the Gold RIng which can be deformed very easily even with application of small amount of force. Malleability refers to materials refers to the ability to be stretched, shaped, or molded through applied pressure. Uses of Aluminium Aluminium is the second most malleable metal. It is widely used in applications including aerospace (the skins of planes), transportation (auto body sheet), packaging (can bodies and ends) and construction (building facades). Uses of Gold Gold is the most malleable material. It is widely ised in Jewellery due to its malleable nature. It is also drawn in form of threads and used for stitching sarees (Kerala is known for such sarees)
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Take a Steel vessel. Fill it half with water and heat it by putting it on a Gas stove and lighting the flame. Notice that the temperature of water starts increasing slowly and after some time the water starts to boil. What led to boiling of water ? How did the heat got transferred to the water when we were heating the steel vessel ?
Experiment 1- Opaque, Transparent and Translucent Objects Take a Torch light in your hand. Move towards the bed in your house. Put the torch light in close contact with the back rest of the bed and switch it on. Observe if any light is coming from the other side of the back rest. You would find that no light is coming from the other end of the back rest. This is because the material i.e. painted wood in this case is an OPAQUE MATERIAL and does not allow light to pass through it. Now take a spectacles that may belong to your father or mother . Put the torch light in close contact with one of the glasses of the spectacles and switch it on. Observe if any light is coming from the other side of the Glass. You would find that light is coming from the other side of the glass. This is because the glass of the spectacles is TRANSPARENT MATERIAL and allows light to pass through them. Now take a piece of A4 Sheet paper that is used for printing/drawing. Put the torch light in close contact with one face of the paper and switch it on. Observe if any light is coming from the other side of the Paper. You would find that some light is coming from the other side of the paper. The amount of light that is coming out is less than the situation when we had experimented by passing light through spectacles. This is because although the glass in spectacles is a TRANSPARENT MATERIAL and allows light to pass through it, but the A4 sheet paper is a TRANSLUCENT MATERIAL and allows only a fraction of light to pass through it. Understanding the Scientific principles behind the existence of Opaque, Transparent and Translucent objects
Yu have seen a Guitar for sure. Pluck one of the strings of the Guitar and observed how the string starts to vibrate. All materials are made of atoms which consist of electrons (negatively charged ions) in the periphery and protons (positively charged ions) at the centre. Electrons of atoms have a natural frequency at which they tend to vibrate. Imagine that electrons were connected to the proton with a spring and you pluck that string similar to the string of the Guitar. What will happen? The atom will start to vibrate. Similar thing happens when light strikes a material. There can be three scenarios: When a light wave with that same natural frequency impinges upon an atom, then the electrons of that atom will be set into vibrational motion. If a light wave of a given frequency strikes a material with electrons having the same vibrational frequencies, then those electrons will absorb the energy of the light wave and transform it into vibrational motion. During its vibration, the electrons interact with neighboring atoms in such a manner as to convert its vibrational energy into thermal energy. Subsequently, the light wave with that given frequency is absorbed by the object, never again to be released in the form of light. So the selective absorption of light by a particular material occurs because the selected frequency of the light wave matches the frequency at which electrons in the atoms of that material vibrate. Such a material is called as TRANSPARENT MATERIAL. What happens when the frequencies of the light waves do not match the natural frequencies of vibration of the objects ? When light waves of these frequencies strike an object, the electrons in the atoms of the object begin vibrating. But instead of vibrating in resonance at a large amplitude, the electrons vibrate for brief periods of time with small amplitudes of vibration; then the energy is re-emitted as a light wave. If the object is transparent, then the vibrations of the electrons are passed on to neighboring atoms through the bulk of the material and re-emitted on the opposite side of the object. This happens in case of TRANSLUCENT MATERIALS. If the object is opaque, then the vibrations of the electrons are not passed from atom to atom through the bulk of the material. Rather the electrons of atoms on the material's surface vibrate for short periods of time and then reemit the energy as a reflected light wave. This happens in case of OPAQUE MATERIALS. |
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