Question

In a concave mirror experiment, an object is placed at a distance x₁ from the focus and the image is formed at a distance x₂ from the focus. The focal length of the mirror would be
(a) $x_1 x_2$
(b) $\sqrt {x_1 x_2}$
(c) $\sqrt \frac{x_1 + x_2}{2}$
(d) $\sqrt \frac{x_1}{x_2}$

Answer 1

$\huge\mathfrak {hola dear}$

Option C is correct

Answer 2

Answer is A.
Object distance is x¹+f and image distance is x²+f, where f is the focal length.
Hence we have
$\frac{1}{x_{1}+f}+ \frac{1}{x_{2}+f}= \frac{1}{f} \\ Solving, \: we \: get \colon \\ f^{2}=x_{1} x_{2} \\ f=\sqrt{x_1 x_2} \\ \huge \textcolor {red}{ \mathfrak {Hope \: this \: helps}}$