There are two lenses having focal length of - 25 cm and + 20 cm. What are the nature of the lenses. Calculate power of each lens and total power of the combination of two lenses.

measuring things 1 litre of water

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explanation:

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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