Two lenses have power +2D and +0.5D. What is the power of the combination of these lenses?

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Solution

Step 1: Given data,
Power of lens one, $P 1 = + 2 D$
Power of lens two, $P 2 = + 0.5 D$
Step 2: Power of the combination of these lenses
The arithmetical total of the powers of two thin lenses in contact is equal to the combined power of the two lenses.
Total power, $P = P 1 + P 2 = 2 + 0.5 = 2.5 D$
Hence, the power of the combination of these lenses is $2.5 D$ .

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