How are power and focal length of a lens related? You are provided with two lenses of focal length 20cm and 40cm respectively. Which lens will you use to obtain more convergent light?
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$\text{P}=\frac{1}{\text{f}(\text{in meter})}=\frac{100}{\text{f}(\text{in cm})}$$\text{f}_1=20\text{cm}\ \therefore\ \text{P}_1=\frac{100}{20}=5.0\text{D}$
$\text{f}_2=40\text{cm}\ \therefore\ \text{P}_2=\frac{100}{40}=2.5\text{D}$
The lens of focal length 20cm or power 5.0D will be used to have more convergent light. This is because lens of small focal length or large power strongly converges the parallel beam of light.
$\text{f}_2=40\text{cm}\ \therefore\ \text{P}_2=\frac{100}{40}=2.5\text{D}$
The lens of focal length 20cm or power 5.0D will be used to have more convergent light. This is because lens of small focal length or large power strongly converges the parallel beam of light.
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