Why does silver turn black or green when it is old? Or, why does a silver coin blacken when exposed to sulphuretted hydrogen? Answer: Air contains small amounts of H2S gas. This H2S gas reacts with silver to produce black-coloured silver sulphide. As a result, gradually, i.e. when old, silver sulphide deposits on shiny silver …
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Explain why do oil paintings turn black when exposed to hydrogen sulphide gas (present in air) due to lead compounds in oil paints. Answer: Oil paints contain lead compounds. This compound reacts with H2S in the air to produce black-coloured lead sulphide (PbS). As a result, the old oil painting becomes black. Pb + H2S …
When the light shines on the mirror, the mirror shines, but when the light shines on the wall of the room, why does the wall not shine? Answer: Because the surface of the mirror is smooth, the light rays are reflected regularly in the mirror. In regular reflection the reflected ray moves in a specific …
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When an air bubble rises from the water, why does the air bubble appear shiny when viewed from the air? Answer: When air rises from the water in the form of a bubble, the bubble appears shiny when viewed from an air medium. This is because light rays fall through the water onto the bubble’s …
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Why does a container full of water appear shallow? Answer: When a container is filled with water, it appears shallower when viewed from above. This is because water is a dense medium and air is a light-medium. Hence the diffracted rays coming from the bottom of the container are refracted from the denser medium to the …
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Why is ground glass clean and shiny when wet with water? Answer: Ground glass is rough. Therefore, the light incident on the ground glass is diffusely reflected. That is why ground glass looks opaque. A thin lining falls on the ground glass when wetted with water. As a result, the rough surface becomes slightly smoothed. …
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If there is a crack in the glass window, why does that place look shiny? Answer: If there is a crack in the glass window, the area looks shiny. Because there is air in the cracks. Rays of light incident from the dense medium of glass to the thin medium of air at an angle …
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Why is mercury coated on the back of the mirror? Answer: Mirror is made of glass. Glass is a transparent material. As a result, when light falls on the glass, most of the incident light rays are refracted through the glass and go to the other side. A very small amount of light is reflected. …
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Why are the pages of the book white and crisp? Answer: As book pages are white, no light is absorbed by the pages. As a result, the texts are clearly visible. Scattered reflection of light occurs due to the roughness of the leaves. As a result, writing can be read from any direction.
Why are cinema screens made white? Answer: As the cinema screen is white, it does not absorb the incident light but reflects almost the entire part. So the picture looks brighter on the white screen. Also, because the white screen reflects all colours of light, the colour of the image does not change. Hence, the …
