Question

In a cathode ray oscillograph, the focusing of beam on the screen is achieved by
A. Convex lens
B. Magnetic lens
C. Electric potential
D. All of those

Answer 1

Hint: Cathode ray oscilloscope is known as CRO. It is used by the student while doing practical. You can see the waveforms of a diode or any device. By looking at waves, we can determine many terms and can get many conclusions by using output waves.

Complete step-by-step answer:
Cathode ray oscilloscopes are also known as CRO. It is an instrument which is used in the laboratory to display, measure, and analyze various waveforms like a triangular wave, square wave, etc. It shows a graph on an X-Y plot and it is a very fast plotter which displays an input signal versus time.
Ray in the oscilloscope uses a luminous spot which is a result of striking a beam of electrons. This spot shows variation as the input varies.
Now the question comes, why the electron beam?
The reason is the low effect of a beam of an electron which is used for obeying the changes in the instantaneous values of continuously changing input waves. To eject an electron or to get an electron beam we need voltage. Therefore CRO works on electric voltage.
Using CRO in the laboratory we can determine time, VPP, amplitude, can change the type of wave frequency over a wide range.
Answer is (C).

Note: To focus electron beams we used two methods, electrostatic focusing and electromagnetic focusing. Do not get confused between CRO and CRT. CRO stands for cathode-ray oscilloscope while CRT stands for cathode ray tube.