What device emits light (electromagnetic radiation), which is usually spatially coherent, through a process called stimulated emission?
What is the name for a net of fine lines or fibres in the eyepiece of a sighting device, such as a telescope, a telescopic sight, a microscope, or the screen of an oscilloscope?
What is the name of a device, consisting essentially of two wires of different metals, whereby heat energy may be changed to electrical energy?
