plz give diagram...
Question is easy
1. at infinity
2. between infinity and optical centre.
when an object is placed at infinity, the two rays ao and bd running parallel to the principal axis get refracted at point o and d respectively and get diverged along the directions ox and dy respectively. these diverged rays i.e. ox and dy appears to intersect each other at the principal focus of the concave lens after extending back by dotted lines. therefore, in case of concave lens when the object is placed at infinity the image is formed at the principal focus, diminished (point sized), virtual and erect.
2. when the object is placed between infinity and optical centre
when an object ab is placed between infinity and optical centre of a concave lens, a ray of light ao is parallel to the principal axis diverges along the direction ox after refraction and appears to come from the principal focus f along the direction of. the other ray of light ac goes straight through the optical centre c of the concave lens without any deviation along the direction cy. as it is clear from the figure (given below) that both the refracted rays i.e. ox and cy are diverging in nature, so these rays appear to intersect each other at point a’ on the left side of the lens on producing back. hence, the image a’b’ formed in case is a virtual image is formed at the same side of the lens, between the optical centre and focus. also the image formed is diminished and erect.
the instantaneous acceleration of the object at t = 2 seconds is