The potential difference that must be applied to stop the fastest photo electrons emitted by a nickel surface, having work function $5.01\, eV$, when ultraviolet light of $200 \,nm$ falls on it, must be
- 2.4V
- -1.2V
- -2.4V
- 1.2V
The Correct Option is B
Solution and Explanation
Incident wavelength, $λ=200 \, nm $
Work function, $\phi _0=5.01 \, eV $
According to Einstein's photoelectric equation
$eV_s=hv-\phi _0$
$eV_s=\frac {hc}{λ}-\phi _0$
where $V_s $ is the stopping potential
$eVs= \frac {(1240 \, eV \, nm)}{(200 \, nm)}-5.01 \, eV $
$\, \, \, \, =6.2eV-5.01 \, eV=1.2 \, eV $
Stopping potential, $V_s=1.2 \, V $
The potential difference that must be applied to
stop photoelectrons $=-V_s=-1.2 \, V $
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Concepts Used:
Electric Current
Defining Electric Current
It is the rate of flow of electrons in a conductor. SI Unit - Ampere (A).
Electrons are negatively charged particles hence when they move a number of charges moves.
Note:- The ability of a particular substance to conduct electricity depends on the number of electrons that are able to move . Some of the materials allow current to flow better than others.
What is an Electromotive Force?
If a force acts on electrons to make them move in a particular direction, then up to some extent random motion of the electrons will be eliminated. An overall movement in one direction. The force which acts on the electrons to move them in a certain direction is known as electromotive force and its quantity is known as voltage and is measured in V.