I found the mention of 'oscillograph' in a numerical under the electrostatics chapter. Pls could you explain to me what this oscillograph actually is??
The light-beam oscillograph has much less weight to move than does the pen-writing instrument and so responds satisfactorily to higher frequencies, about 500 Hz, or cycles per second, compared with 100 Hz for the pen assembly. It uses a coil to which a small mirror is attached. A beam of light is reflected from the mirror onto a photographic film moving at a constant speed. The cathode-ray oscillograph makes use of a sharply focused electron beam to display the relationship between variable quantities on a luminescent screen similar to that used in a television. It may be either a three- or a four-dimensional recording device, the latter being very versatile. Recording is by transfer of energy to a light-sensitive record, using either an optical-lens system or a fibre-optic faceplate. It can be employed at frequencies in the megahertz range.