Numerical aperture is constant in case of step index fiber.

The correct answer is False.

Numerical aperture (NA) is a measure of the light-gathering ability of an optical system. It is defined as the sine of the half-angle of the cone of light that can be accepted by the system. In the case of a step-index fiber, NA is not constant. It depends on the refractive indices of the core and cladding materials, as well as the diameter of the fiber.

The refractive index of a material is a measure of how much light bends when it passes from one material to another. The refractive indices of the core and cladding materials are