Question

Light striking a metal plate can eject electrons from the plate's surface (this is called the photoelectric effect). Imagine that we place the plate in a vacuum and set up an electric field in the plate's vicinity that is uniform in magnitude and direction such that the electric field vector E at any point near the plate has a magnitude of 1000 N/C and points directly away from the plate, perpendicular to its surface. Electrons ejected by the photoelectric effect will have initial kinetic energies of no more than about 3 eV, where 1 eV = 1.6 x 10^-19 J. Roughly estimate the maximum distance that an ejected electron can get from the plate under these circumstances. (Hint: Consider an analogy to the behavoir of a thrown ball in a uniform gravitational field.)

Answer 1

Answer: The kinetic energy in physics can be defined as the energy possessed by the body when it is in motion relatively to the other bodies. This energy depends on the mass of the body and the square of the velocity. Its measurable unit is in Joules.

Answer and Explanation:

Given data:

The electric field is

E

=

1000

N

/

C

The initial kinetic energy of the ejected electrons is

k

=

3

e

V

=

(

3

×

1.6

×

10

−

19

)

J

The expression for the conservation of energy of the electrons is given by

k

=

U

p

k

=

e

V

Here

U

p

=

e

V

is the potential energy of the electron

Here

V

=

E

d

is the electric potential in electric field

Here

e

=

1.6

×

10

−

19

C

is the charge of the electon

Substituting the values in the above equation as,

k

=

q

V

k

=

e

(

E

d

)

(

3

×

1.6

×

10

−

19

J

)

=

(

1.6

×

10

−

19

C

)

(

1000

N

/

C

)

×

d

d

=

0.003

m

d

=

3

m

m

Explanation: