Parallel rays of light entering a convex lens converge at:
Principal focus
Secondary focus
Centre of curvature
Optical centre
A ray of light after refraction through a lens emerges parallel to the principal axis of the lens. The incident ray passes through :
(a) its optical centre
(b) its first focus
(c) its second focus
(d) the centre of curvature of the first surface.
(a) With the help of a labelled diagram, explain how a concave lens diverges a beam of parallel light rays. Mark the principal axis, optical centre, principal focus and focal length of the concave lens on the diagram. (b) State whether concave lens has a real focus or a virtual focus. (c) List some things that concave lens and convex mirror have in common.
A ray light incident on a lens parallel to its principal axis, after refraction passes through or appears to come from :
(a) its first focus
(b) its optical centre
(d) the centre of curvation of its second surface.