(a) If the image formed by a lens is diminished in size and erect, for all positions of the object, then the lens is a concave lens.
(b) The point on the lens through which a ray of light passes undeviated is known as Pole.
(c) 1f=1v−1u⇒1v=1f+1u⇒v=u×fu+f;f=20cm, u=−30 cm
(i) V=(−30)×2020−30=60 cm
The image is formed at a distance of 60 cm on the other side of the optical centre
(iii) Image formed is inverted.
(a) The image is formed by a large number of rays from the object. So, even if one half of the lens is darkened, the image will form. However, the brightness of the image will be less as compared to that of the image formed without wrapping the lens.
(iii) Negative sign indicates that the image is real and inverted.