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4 (a) (i) Which lens is a converging lens with the greatest power? [Insert figure reference here] (ii) The equation that relates the power of a lens to the focal length of the lens is power (in dioptres) = \( \frac{1}{focal \ length \ (in \ metres)} \) The power of a lens is 5 dioptres - Edexcel - GCSE Physics - Question 4 - 2019 - Paper 1

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4-(a)-(i)-Which-lens-is-a-converging-lens-with-the-greatest-power?--[Insert-figure-reference-here]--(ii)-The-equation-that-relates-the-power-of-a-lens-to-the-focal-length-of-the-lens-is--power-(in-dioptres)-=-\(-\frac{1}{focal-\-length-\-(in-\-metres)}-\)--The-power-of-a-lens-is-5-dioptres-Edexcel-GCSE Physics-Question 4-2019-Paper 1.png

4 (a) (i) Which lens is a converging lens with the greatest power? [Insert figure reference here] (ii) The equation that relates the power of a lens to the focal l... show full transcript

Worked Solution & Example Answer:4 (a) (i) Which lens is a converging lens with the greatest power? [Insert figure reference here] (ii) The equation that relates the power of a lens to the focal length of the lens is power (in dioptres) = \( \frac{1}{focal \ length \ (in \ metres)} \) The power of a lens is 5 dioptres - Edexcel - GCSE Physics - Question 4 - 2019 - Paper 1

Step 1

Which lens is a converging lens with the greatest power?

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Answer

To determine which lens has the greatest power, we need to recall that the power of a lens is defined as the reciprocal of its focal length in meters. The shorter the focal length, the higher the power. From the given options A, B, C, and D, we can visually assess each lens's shape and determine which has the shortest focal length. In general, the lens that is more strongly converging will have a more bulbous shape, leading to a shorter focal length. Hence, the answer can be determined visually from the diagram.

Step 2

Use the equation to calculate the focal length of the lens in cm.

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Answer

Given the power of the lens is 5 dioptres, we can use the formula:

P=1fP = \frac{1}{f}

where (P) is the power in dioptres and (f) is the focal length in meters. Rearranging gives:

f=1Pf = \frac{1}{P}

Substituting in the given power:

f=15=0.2 mf = \frac{1}{5} = 0.2 \text{ m}

To convert this to centimeters, we multiply by 100:

f=0.2×100=20 cmf = 0.2 \times 100 = 20 \text{ cm}

Thus, the focal length of the lens is 20 cm.

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