In a cathode ray tube, the function of the x-plates is to

Step 1: Analyze the question The question asks about the role of the X-plates in a cathode ray tube (CRT), such as the one in an old oscilloscope or TV.

Step 2: Explain the concept A CRT has these main parts:

• Electron gun: produces and accelerates a beam of electrons.
• Deflecting plates: two pairs of parallel metal plates that steer the beam using electric fields. • X-plates are arranged vertically, one on the left and one on the right. The voltage across them creates a horizontal electric field, which pushes the beam sideways (horizontally). • Y-plates are arranged horizontally, one on top and one below. They create a vertical field, which moves the beam up and down (vertically).
• Fluorescent screen: glows where the electrons strike it.

Step 3: Solution

• In an oscilloscope, the X-plates are connected to the time-base, a sawtooth voltage that sweeps the spot across the screen at a steady rate. This is horizontal deflection.
• The Y-plates receive the input signal, which shows up as vertical deflection.

Checking the options:

• A. Deflect the beam horizontally. Correct.
• B. Deflect the beam vertically. This is the job of the Y-plates.
• C. Reflect the beam. The plates deflect the beam; they do not reflect it.
• D. Generate sinusoid waves. The plates do not generate any waves. They only respond to applied voltages.

Step 4: Answer The X-plates deflect the electron beam horizontally, so the answer is A.

Tip: Remember "X is across, Y is up." X-plates move the spot along the x-axis (horizontal), and Y-plates move it along the y-axis (vertical), just like a graph.