Two thin equiconvex lenses each of focal length 0.2 m are placed coaxially with their optic centres 0.5m apart. Then find the focal length of the combination.

Explanation

To find the focal length of the combination of two thin equiconvex lenses placed coaxially, we can use the lens formula for two lenses separated by a distance. The formula is given by:

\[ \frac{1}{f} = \frac{1}{f_1} + \frac{1}{f_2} - \frac{d}{f_1 f_2} \]

Where:
- \( f \) is the focal length of the combination,
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