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CONVEX LENS Convex lens is thicker at the centre and thinner at the edges. An optical lens is generally made up of two spherical surfaces. If those surfaces are bent outwards, the lens is called a  biconvex lens  or simply convex lens. These type of lenses can converge a beam of light coming from outside and focus it to a point on the other side. This point is known as the focus and the distance between the centre of the lens to the focus is called the  focal length of convex lens.  However, if one of the surfaces is flat and the other convex, then it is called a  plano-convex lens. Difference between convex and concave lens: There is another type of lens known as concave lens. The major differences between the two are: CONVEX CONCAVE This lens converges a straight beam of light. This lens diverges a straight beam of light. This lens is thicker at the centre and gets thinner as we move towards the edges. This lens is thinner at the centre and gets thicke
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wax fire

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A  wax fire  is created when melted or boiling  wax  is doused in water.   In the case of wax melted down, only the top surface has access to oxygen, so the fire progresses slowly. When water is added to the wax, two things happen. Firstly, the water — being denser than wax — sinks to the bottom of the container. Secondly, as burning wax quickly reaches a temperature of well over 200 degrees C, the water instantly vapourises. When water changes from a liquid to a gas, there is more than a thousand-fold increase in volume. The water expands violently, and throws the hot wax layer above it into the air as small droplets. The wax now has a much bigger surface area exposed to oxygen so combustion takes place very quickly.
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