Reflection by Spherical Mirrors: Practice Problem & Solution

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Reflection by Spherical Mirrors. Understanding the underlying formula is key to arriving at the correct answer below:

The rod's closer end is at $u_1 = -20 cm$ (which is $2f$ since $f = -10 cm$ ). The image of this end forms at the center of curvature, $v_1 = -20 cm$ . The farther end is at $u_2 = -30 cm$ . Its image is at $v_2 = \frac{u_2 f}{u_2 - f} = \frac{(-30)(-10)}{-30 - (-10)} = \frac{300}{-20} = -15 cm$ . The length of the image is $|v_1 - v_2| = |-20 - (-15)| = 5 cm$ .