The Student Room Group

Aiming an Oscilloscope Beam

The bright lines on an oscilloscope are due to electrons hitting the phosphorescent screen. The electrons are first accelerated by an electric field to form a horizontal beam, then deflected by a horizontal and a vertical electric field. The horizontal electric field is used to "sweep" the electron beam across the screen over a certain period of time, while the vertical electric field is controlled by the signal that is being measured.

In one oscilloscope, the electrons are initially accelerated from rest across a potential difference of V.

What is the speed u of the electron after initial acceleration? Ignore relativistic effects.

The electron has mass m
e

and charge e.

PART B
The vertical deflection field is modelled as a constant electric field of magnitude E, with a horizontal extent of d. If the electrons strike the screen at height h below the centre point of the original beam, what is the distance L to the screen from the end of the deflecting electric field?
Original post by zafarrescue6
The bright lines on an oscilloscope are due to electrons hitting the phosphorescent screen. The electrons are first accelerated by an electric field to form a horizontal beam, then deflected by a horizontal and a vertical electric field. The horizontal electric field is used to "sweep" the electron beam across the screen over a certain period of time, while the vertical electric field is controlled by the signal that is being measured.

In one oscilloscope, the electrons are initially accelerated from rest across a potential difference of V.

What is the speed u of the electron after initial acceleration? Ignore relativistic effects.

The electron has mass m
e

and charge e.

PART B
The vertical deflection field is modelled as a constant electric field of magnitude E, with a horizontal extent of d. If the electrons strike the screen at height h below the centre point of the original beam, what is the distance L to the screen from the end of the deflecting electric field?


As this problem is from IsaacPhysics, it would be better if you included the link to the problem in future. The formatting of the variables goes haywire and can be annoying.
https://isaacphysics.org/questions/an_oscilloscope_sym?stage=all

Please don't just copy and paste the problem without describing what you have.

Part B
Hint 3 seems to be useful and has helped you break down the problem.
When the electron is subjected to the electric field, it undergoes projectile motion and it is the vertical velocity that changes.
When the electron exits the electric field, it undergoes straight-line motion.
(edited 2 months ago)
Reply 2
I am still confused don't know how to proceed
Original post by zafarrescue6
I am still confused don't know how to proceed

Please describe or explain something useful.
What do you understand about the problem? I mean the physics.

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