a) Define 1 dioptre of power of a lens b) The refractive index of diamond is 2.42. What is the meaning of this statement. c) In which type of lens linear magnification is always less than one ?

a) Define 1 dioptre of power of a lens b) The refractive index of dia

1.	a) Define 1 dioptre of power of a lens b) The refractive index of diamond is 2.42. What is the meaning of this statement. c) In which type of lens linear magnification is always less than one ?
Answer» Solution :a) The SI unit of POWER of lens is dioptre which is denoted by the letter D. 1 Dioptre is defined as the power of a lens of FOCAL length 1 meter. b) The refractive index of diamond is 2.42 this means that the speed of light in diamond will reduce by a factor of 2.42 as compared to its speed in AIR. In other words the speed of light in diamond is 2.42 times less than the normal speed of light in vacuum. c) Concave lens always has linear magnification less than ONE, because it always gives diminished images.