282513 The focal length of the objective of a terrestrial telescope is \(80 \mathrm{~cm}\) and it is adjusted for parallel rays, then its power is 20 . If the focal length of erecting lens is \(20 \mathrm{~cm}\), then full length of the telescope will be

282505 The plane faces of two identical plano-convex lenses each having a focal length of \(50 \mathrm{~cm}\) are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is :

282506 Two thin lenses of focal length \(20 \mathrm{~cm}\) and \(25 \mathrm{~cm}\) are in contact. The effective power of the combination is :

282507 The distance between an object and the screen is \(100 \mathrm{~cm}\). A lens produces an image on the screen when placed at either of two positions 40 \(\mathrm{cm}\) apart. The power of the lens is approximately

282513 The focal length of the objective of a terrestrial telescope is \(80 \mathrm{~cm}\) and it is adjusted for parallel rays, then its power is 20 . If the focal length of erecting lens is \(20 \mathrm{~cm}\), then full length of the telescope will be

282505 The plane faces of two identical plano-convex lenses each having a focal length of \(50 \mathrm{~cm}\) are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is :

282506 Two thin lenses of focal length \(20 \mathrm{~cm}\) and \(25 \mathrm{~cm}\) are in contact. The effective power of the combination is :

282507 The distance between an object and the screen is \(100 \mathrm{~cm}\). A lens produces an image on the screen when placed at either of two positions 40 \(\mathrm{cm}\) apart. The power of the lens is approximately

282513 The focal length of the objective of a terrestrial telescope is \(80 \mathrm{~cm}\) and it is adjusted for parallel rays, then its power is 20 . If the focal length of erecting lens is \(20 \mathrm{~cm}\), then full length of the telescope will be

282505 The plane faces of two identical plano-convex lenses each having a focal length of \(50 \mathrm{~cm}\) are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is :

282506 Two thin lenses of focal length \(20 \mathrm{~cm}\) and \(25 \mathrm{~cm}\) are in contact. The effective power of the combination is :

282507 The distance between an object and the screen is \(100 \mathrm{~cm}\). A lens produces an image on the screen when placed at either of two positions 40 \(\mathrm{cm}\) apart. The power of the lens is approximately

282513 The focal length of the objective of a terrestrial telescope is \(80 \mathrm{~cm}\) and it is adjusted for parallel rays, then its power is 20 . If the focal length of erecting lens is \(20 \mathrm{~cm}\), then full length of the telescope will be

282505 The plane faces of two identical plano-convex lenses each having a focal length of \(50 \mathrm{~cm}\) are placed against each other to form a usual biconvex lens. The distance from this lens combination at which an object must be placed to obtain a real, inverted image which has the same size as the object is :

282506 Two thin lenses of focal length \(20 \mathrm{~cm}\) and \(25 \mathrm{~cm}\) are in contact. The effective power of the combination is :

282507 The distance between an object and the screen is \(100 \mathrm{~cm}\). A lens produces an image on the screen when placed at either of two positions 40 \(\mathrm{cm}\) apart. The power of the lens is approximately