Question

An object is placed at a distance 30 cm from a concave lens of focal length 30

cm

i) Use lens formula to determine the distance of the image from

the lens.

ii) List four characteristics of the image ( nature, position, size,

erect/ inverted) in this case.

iii) Draw a labelled diagram to justify your answer of part (ii)​

Answer 1

concave lens produces a virtual, erect diminished image.

concave lens produces a virtual, erect diminished image.Using Real Is Positive RIP Convention, u=30 and f=-15

concave lens produces a virtual, erect diminished image.Using Real Is Positive RIP Convention, u=30 and f=-151/u+1/v=1/f

concave lens produces a virtual, erect diminished image.Using Real Is Positive RIP Convention, u=30 and f=-151/u+1/v=1/f1/30+1/v=−1/30

1/v=−1/30−1/30=−3/30=−1/10

−1/30=−3/30=−1/10v=−10M=v/u=−1/3

−1/30=−3/30=−1/10v=−10M=v/u=−1/3So image is erect, virtual, 1/3 size of object, and 10 cm from the lens, (between lens and object)