When an object is placed at a distance of $25cm$ from a spherical mirror, the magnification is $m_1$. When the object is moved $15cm$ away from mirror with respect to the earlier position, then magnification becomes $m_2$. If $\frac{m_1}{m_2}=4$, then the focal length of the mirror is :

Q. When an object is placed at a distance of $25\text{cm}$ from a mirror, the magnification is $m_1$. But the magnification becomes $m_2$ when the object is moved $15\text{cm}$ farther away from the mirror with respect to earlier position. If $\frac{m_1}{m_2}=4$, then find the focal length of the mirror and its nature.

Q. When an object is placed at a distance of $25\text{cm}$ from a mirror, the magnification of the real image formed is $m_1$. When the object is moved $15\text{cm}$ away with respect to the earlier position along the principal axis, magnification becomes $m_2$. If $m_1\times m_2=4$, the focal length of the mirror in $\text{cm}$ is $P\times 10$. Then, find the value of $P$

Q. When an object is placed at a distance of $25\text{cm}$ from a mirror, the magnification is $m_1.$ The object is moved $15\text{cm}$ away with respect to the earlier position along principal axis, magnification becomes $m_2.$ If $\frac{m_1}{m_2}=4.$ The magnitude of focal length of the mirror in $\text{cm}$ is $n\times 10\text{cm}.$ The value of $n$ is (integer only)

Q. If an object is placed at a distance of 20cm from the pole of a concave mirror, the magnification of its real image is 3. If the object is moved away from the mirror by 10cm, then the magnification is -1.

Q. Consider a concave mirror and a convex lens (refractive index = 1.5) of focal length $10\text{cm}$ each, separated by a distance of $50\text{cm}$ in air as shown in the figure. An object is placed at a distance of $15\text{cm}$ from the mirror. Its erect image formed by this combination has magnification $M_1$.When the set up is kept in a medium of refractive index $\frac{7}{6}$, the magnification becomes $M_2$. The magnitude of $\left|\frac{M_2}{M_1}\right|$ is