By which type of mirror,the image obtained is always erect?

In the figure shown,a point object $O$ is placed in air on the principal axis. The radius of curvature of the spherical surface is $60\, cm$. Let $I_f$ be the final image formed after all the refractions and reflections. Which of the following statements is correct?

Three plane mirrors form an equilateral triangle with each side of length $L$. There is a small hole at a distance $l > 0$ from one of the corners as shown in the figure. $A$ ray of light is passed through the hole at an angle $\theta$ and can only come out through the same hole. The cross section of the mirror configuration and the ray of light lie on the same plane.
Which of the following statement(s) is(are) correct?
$(A)$ The ray of light will come out for $\theta=30^{\circ}$, for $0 < l < L$.
$(B)$ There is an angle for $l=\frac{L}{2}$ at which the ray of light will come out after two reflections.
$(C)$ The ray of light will $NEVER$ come out for $\theta=60^{\circ}$, and $l=\frac{L}{3}$.
$(D)$ The ray of light will come out for $\theta=60^{\circ}$, and $0 < l < \frac{L}{2}$ after six reflections.

$A$ reflecting surface is represented by the equation $y = \frac{2L}{\pi} \sin \left( \frac{\pi x}{L} \right)$,$0 \leq x \leq L$. $A$ ray travelling horizontally becomes vertical after reflection. The coordinates of the point$(s)$ where this ray is incident is?

Discuss the sign convention of distances for reflection by a spherical mirror and refraction by a spherical lens.

$A$ small lamp is hung at a height of $8 \text{ feet}$ above the centre of a round table of diameter $16 \text{ feet}$. The ratio of intensities of illumination at the centre and at points on the circumference of the table will be