CRT's question

Question

In a CRT, the deflection on the screen is 2.4 cm when the accelerating voltage is 480 V and the deflecting voltage is 36 V. What deflection will you see in the screen if the accelerating voltage is 960 V and the deflecting voltage is 18 V?

Answer 1

KE_{1 = eV1}   

KE_{2  =} eV2

Where V is accelerating voltage applied on electrons

y_{1is deflection on screen in first case and y2 in second case}

y₁ = 2.4 cm

y_{2  =?}

 

V₁ = 480 Volt =accelerating voltage 1

v_{2   = 960 Volt  = accelerating voltage  2}

 

 

Deflecting Voltage 1 = 36 Volt

Deflecting Voltage 2 = 18 Volt

Electric Field 1 =36/d

Electric Field 2 = 18/d

Force1 = eE1 = e36/d

Force2 =eE2  = e19/d 

 

as E = V/D  Where V is deflecting voltage

 

 

assuming horizontal distance to be equal

y₁/y_{2 =(36/18)x(960/480)}

         =4

y₂ = 4 y ₁

 

y₂ = 4x2.4 = 9.6 cm