When a number of thin lenses of focal lengths `[f_(1),f_(2),f_(3)......"` are in contact,then effective focal length is

Two thin lenses of focal lengths f_(1) and f_(2) are in contact. The focal length of this combination is

Power (P) of a lens is given by reciprocal of focal length (f) of the lens. i.e. P = 1//f . When f is in metre, P is in dioptre. For a convex lens, power is positive and for a concave lens, power is negative. When a number of thin lenses of powers p_(1), p_(2), p_(3).... are held in contact with one another, the power of the combination is given by algebraic sum of the powers of all the lenses i.e., P = p_(1) + p_(2) + p_(3) + ........ Answer the following questions : Focal length of the combined three lenses would be

Power (P) of a lens is given by reciprocal of focal length (f) of the lens. i.e. P = 1//f . When f is in metre, P is in dioptre. For a convex lens, power is positive and for a concave lens, power is negative. When a number of thin lenses of powers p_(1), p_(2), p_(3).... are held in contact with one another, the power of the combination is given by algebraic sum of the powers of all the lenses i.e., P = p_(1) + p_(2) + p_(3) + ........ Answer the following questions : When a third lens of focal length - 20 cm is placed in contact with the two lenses, power of the three would be

Power (P) of a lens is given by reciprocal of focal length (f) of the lens. i.e. P = 1//f . When f is in metre, P is in dioptre. For a convex lens, power is positive and for a concave lens, power is negative. When a number of thin lenses of powers p_(1), p_(2), p_(3).... are held in contact with one another, the power of the combination is given by algebraic sum of the powers of all the lenses i.e., P = p_(1) + p_(2) + p_(3) + ........ Answer the following questions : Two thin lenses are in contact and the focal length of the combination is 80 cm . If the focal length of one lens is 20 cm , the focal length of the other would be

Two thin lenses of focal length f_(1) and f_(2) are in contact and coaxial. The power of the combination is

Two thin convex lenses of focal lengths f_(1) and f_(2) are in contact and coaxial. The power of the combination is