A Numerical from Combination of thin lenses in contact

Two thin lenses of focal lengths f1=20cm and f2=60cm are placed in contact. find the focal length f3 of the combined lenses. find also the focal length f of a third lens placed in contact with these two that would result in overall focal length f11=-40cm. (Asked Young) Incoming search terms:class 9 science sample paper for [...]

Can you answer this questions from units and dimensions

“Find the value of 60 joule per minute on a system which has 10cm, 100gm and 1 minute as fundamental units.” Post your answer as comments. You can also upload a file using the contact page or ask a question page. Incoming search terms:questions on units and dimensionsnumericals on units & dimensions in 11 physicsphysics [...]