What type of image is always formed by a concave lens?

Draw a labelled ray diagram to locate the image of an object formed by a convex lens of focal length $20 \, cm$ when the object is placed $30 \, cm$ away from the lens.

When light rays parallel to the principal axis fall on a convex lens,they refract and converge at a point on the principal axis. What is this point called?

The figure below shows a lens treated as a combination of two prisms and a glass block. $(i)$ Name the lens formed by the combination. $(ii)$ Is the lens converging or diverging? $(iii)$ Draw the refraction of two incident rays to illustrate the property of the lens mentioned by you in part $(ii).$

Which of the following has the minimum refractive index?

If the magnification of an image formed by a mirror is $(-\frac{1}{3})$,what type of mirror is it?