Ray Diagram Trick: Image Location in a Flash! ⚡

Struggling to draw ray diagrams and find the image location with lenses? Here's a mind-blowing trick to predict it!

Subject: optics • Classes: 6–12 • Difficulty: intermediate (9-10)

The Trick

For a converging lens, if the object distance ($u$) is given, use the lens formula: $\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$, where $f$ is the focal length and $v$ is the image distance. The trick is to rewrite this as: $\frac{1}{v} = \frac{1}{f} + \frac{1}{u}$. Think of 'image' (v) as the 'sum' of the reciprocals of focal length and object distance. This avoids subtracting fractions, making the calculation faster. Remember to use sign conventions (u is usually negative).

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