Work Function

Q.

What is the work function of an electron?

Q. The work function of the target material is $1.24eV$ and the wavelength of incident light is $4360\stackrel{\circ }{A}$. What retarding potential is necessary to stop the emission of the electrons?

1. $1.61V$
2. $2.61V$
3. $3.61V$
4. $4.61V$

Q.

The wavelength of an X-ray beam is $10\AA$. The mass of a fictitious particle having the same energy as that of the X-ray photons is $\left(\raisebox{1ex}{$xh$}\!\left/ \!\raisebox{-1ex}{$3$}\right.\right)$ kg. The value of $x$ is _______.

Q.

Sodium has a work function of 2.28 eV. Let's say, I introduce a very strong external electric field, which is applying a force on the electrons outwards, thus giving them electrical potential energy of 1.5 eV each. What is the work function of the metal surface in such a case?

1. 0 eV

2. 1.5 eV

3. 0.78 eV

4. 2.28 eV

Q.

Why does coal appear black in white light?

Q. The work function for aluminium surface is 4.2 eV and that for sodium surface is 2.0 eV. The two metals were illuminated with appropriate radiations so as to cause photoemission. Then choose the correct statement.

1. Both aluminium and sodium will have the same threshold frequency.
   
2. The threshold frequency of aluminium will be more than that of sodium.
   
3. The threshold frequency of aluminum will be less than that of sodium.
   
4. Cannot say

Q. The maximum velocity of electrons emitted from a metal surface is $v$. What would be the maximum velocity if frequency of the light is increased by a factor of 4?

1. 2$v$
2. > 2$v$
3. < 2$v$
4. between 2$v$ and 4$v$

Q. If an electron recieves 10eV. energy and wastes 3 eV in overcoming the work function then find the potential that will stop the electron from striking the collector plate.

1. 3 V
2. 5 V
3. 7 V
4. 10 V

Q.

Sodium has a work function of 2.28 eV. Let's say, I introduce a very strong external electric field, which is applying a force on the electrons outwards, thus giving them electrical potential energy of 1.5 eV each. What is the work function of the metal surface in such a case?

1. 0.78 eV

2. 1.5 eV

3. 2.28 eV

4. 0 eV

Q.

$\begin{array}{cc}ColumnI& ColumnII\\ \text{(A) If v (frequency) is increased keeping}\text{I (intensity) and}\Phi \text{(work function) constant}& \text{(P) Stoping potential increases}\\ \left(B\right)\text{If I is increased keeping v and}\Phi \text{constant}& \text{(Q) Saturation photocurrent increases}\\ \text{(C) If the distance between anode and cathode increases.}& \text{(R) Maximum KE of the photoelectrons increase}\\ \text{(D) If}\Phi \text{is decreased keeping v and I constant}& \text{(S) Stopping potential remains the same}\end{array}$

1. (A) (P, R); (B) (Q, S); (C) (S); (D) (P, R)

2. (A) (Q, S); (B) (P, R); (C) (S); (D) (P, R)

3. (A) (P, R); (B) (Q, S); (C) (P, R); (D) (S)

4. (A) (P, R); (B) (S); (C) (Q, S); (D) (P, R)

Q.

The photoelectric thresshold wavelength of silver is $3250\times {10}^{-10}m$. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength $2536\times {10}^{-10}m$ is approximately
(Given $h=4.14\times {10}^{-15}eV$ and $c=3\times {10}^{8}m{s}^{-1}$)

1. $0.3\times {10}^{6}m{s}^{-1}$
2. $6\times {10}^{5}m{s}^{-1}$
3. $6\times {10}^{6}m{s}^{-1}$
4. $61\times {10}^{3}m{s}^{-1}$

Q. Five elements $A,B,C,D$ and $E$ have work functions $1.2eV,2.4eV,3.6eV,4.8eV$ and $6eV$ respectively. If light of wavelength $4000\stackrel{\circ }{A}$ is allowed to fall on these elements, then photoelectrons are emitted by

1. $A,B$ and $C$
2. $A,B,C,D$ and $E$
3. $A$ and $B$
4. Only $E$

Q. The work functions for metals A, B and C are $1.92eV,2.0eV$ and $5.0eV$ respectively. According to Einstein’s equation, the metals which will emit photoelectrons for a radiation of wavelength $4100A^{\circ }$ is/are

1. None
2. A only
3. A and B only
4. All the three metals

Q.

The minimum energy required to remove an electron is called

1. Stopping potential

2. Kinetic energy

3. Work function

4. None of these