If on applying cartesian sign convention for spherical lenses, the image distacnce obtained is negative, state the significance of the negative sign.

Draw a simple circuit of a CE transistor amplifier. Explain its working. Show that the voltage gain, A_V of the amplifier is given by A_v = - ( beta_(ac) R_L )/(r_i) where beta_(Ac) is the current gain, R_L is the load resistance and r_1 is the input resistance of the transistor. What is the significance of the negative sign in the expression for the voltage gain?

What are new cartesian sign coventions used for reflectionin spherical mirror? What is the mirror formula?

By stating the sign conventions and assumptions used, derive the relation between distance of object, distance of image and radius of curvature of convex spherical surfaces, when refraction takes from optically rarer to optically denser medium.

By giving sign-conventions, derive the lens formula relating object distance, image distance and focal length for a thin convex lens. Draw a ray diagram to show the formation of image of an object placed between optical centre and focus of a convex lens.