Convex Lens Focal Length – Rankers Physics

Lens Makers Formula/ Len's Formula: Practice Problem & Solution

An object is mounted on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens placed between these walls. The lens is kept at distance \(x\) in front of the second wall. The required focal length of the lens will be
\(\frac{x}{2}\)
\(\frac{x}{4}\)
Less than \(\frac{x}{4}\)
\(\frac{x}{4}\) but less than \(\frac{x}{2}\)

Solution Explained:

To solve this problem, we apply the core principles of Lens Makers Formula/ Len's Formula. Understanding the underlying formula is key to arriving at the correct answer below:

To get a real image of the same size, the image distance from the lens must be \(v = 2f\). Here, \(v = x\), therefore \(x = 2f ⇒ f = \frac{x}{2}\).

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