346 Image FormationQ36.6For definiteness, we consider real objects (p>0).(a)For Mqp=−to be negative, qmust be positive. This will happen in 111qfpif pf>, if theobject is farther than the focal point.(b)For Mqpto be positive, qmust be negative.From we need <.(c)For a real image, qmust be positive.As in part (a), it is sufficient for pto be larger than f.(d)For q<0 we need <.(e)For M>1, we consider separatelyM<−1 and M>1.If Mqp=− <−1, we needqp>1orqp>or11<From pq f+=,pp f+>or21>orpf2<or<2.Now if −>qprorwe may require q<0, since thenpfqwith10f>gives pq>−
This is the end of the preview.
access the rest of the document.