......is called natural optical instrument.

Answer the following questions: Ray optics is based on the assumption that light travels in a straight line. Diffraction effects (observed when light propagates through small apertures/slits or around small obstacles) disprove this assumption. Yet the ray optics assumption is so commonly used in understanding location and several other properties of images in optical instruments. What is the justification?

What for are the optical instruments used?

What is an optical fibre?

Define resolving power of an optical instrument. How does it depend on wavelength?

An optical instrument uses a lens of power 100 D for objective lens and 50 D for its eyepiece. When the tube length is kept at 25 cm, the final is formed at infinity. Identity the optical instrument.

What do you mean by optical instruments? Name any two.

What is a pace maker? Why is it called life-saving instrument?