Besides a diagram, you can also use the Thin Lens Equation and the Magnification Equation to determine characteristics of an image in curved lens (converging and diverging).

The Thin Lens Equation

1 / d₀ + 1 / d_i = 1 / f

Where

d₀ = distance from the object to the optical centre
d_i = distance from the image to the optical centre
f = focal length of the lens; distance from the optical centre to the principal focus

Object distances (d₀) are always positive
Image distances (d_i) are positive for real images (opposite side) and negative for virtual (same side)
The focal length is positive for converging lenses and negative for diverging lenses

The Magnification Equation

M = h_i / h₀ = - d_i / d₀

• Object height (h₀) is positive
• Image height (h_i) is positive for an upright image and negative for an inverted image