Question

Questions can the
above method be used for determining focal length of a) concave lens b) plano concave lens
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Answer 1

Answer:

b) Plano concave lens.

only one side is being curved

and the other side is plane .

Answer 2

Formula for determining the focal lengths are given below.

Explanation:

Basically, the convex lens is the lens of converging property and plano convex lens is the lens to converge parallel rays.

The formula of focal length for the concave lens.

                    ⇒ $\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

Where, f is the focal length, u is the object distance and the v is the image distance.

For plano convex,

                                ⇒ $\frac{1}{f} =$ (n-1) ($\frac{1}{R} +\frac{1}{r}$)

Here, R is the radius of curvature to convex side and r is of infinity side.