Work Function

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. The work function of a substance is $4eV$. The longest wavelength of light that can cause photoelectron emission from this substance is approximately.

1. 540 nm
2. 310 nm
3. 220 nm
4. 400 nm

Q. At a place, a light wave described by the equation $E=\left(\frac{100V}{m}\right)\left[\text{sin}\right(2\pi \times {10}^{15}{s}^{-1})t+\text{sin}(3\pi \times {10}^{15}{s}^{-1}\left)t\right]$, where $t$ is in seconds, falls on a metal surface having work function $2.1\text{eV}$. The maximum kinetic energy of the emitted photoelectrons( in $\text{eV}$) is nearly.

Q.

If work function of a metal is 2 eV, it means every electron requires only 2 eV to get ejected from the metal surface.

1. True

2. False

Q.

Consider a small metallic plate of chromium, having only 5 free electrons on the surface. We shine light on the plate and we observe that these electrons come out but with different energies.

The energy received by each electron is 10 eV. Below is the list of energies with which each electron comes out.

e1 = 2.5 eV.

e2 = 2.7 eV.

e3 = 4.5 eV.

e4 = 5.5 eV.

e5 = 4.7 eV.

If one of these electrons has most optimally used the energy provided to come out, then what could be the work function of the metal chromium?

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Q. A metal has a work function of $2.5\times {10}^{-19}J.$The threshold frequency beyond which photo electrons will come out is.

1. $2.3\times {10}^{14}Hz$
2. $3.3\times {10}^{14}Hz$
3. $2.8\times {10}^{14}Hz$
4. $3.8\times {10}^{14}Hz$

Q. No photoelectrons are emitted from a metal if the wavelength of light exceeds $6000\stackrel{\circ }{A}$. The work function of the metal is approximately equal to

1. $3\times {10}^{-16}J$
2. $3\times {10}^{-19}J$
3. $3\times {10}^{-20}J$
4. $3\times {10}^{-22}J$