Q.

An electron is made to enters symmetrically between two parallel and equally but oppositely charged metal plates, each of 10 cm length. The electron emerges out of the field region with a horizontal component of velocity 106 m/s. If the magnitude of the electric field between the plates is 9.1 V/cm, then the vertical component of velocity of electron is (mass of electron = 9.1×10–31 kg and charge of electron = 1.6×10–19)          [2025]

1 1×106 m/s  
2 0  
3 16×106 m  
4 16×104 m/s  

Ans.

(3)

Horizontal component of velocity will remain same.

⇒ t=lVx=10×10–2106=10–7

⇒ Vy=uy+ayt ⇒ Vy=0+eEm×10–7

⇒ Vy=1.6×10–199.1×10–31×9.1×10+2×10–7

⇒ Vy=16×106 m/s