Stopping Potential vs Frequency

Q.

How to calculate phase difference between the two waves?

Q. An electron moves a dis†an ce of 6.0 cm when aacelerated from rest by an electric field of strength 2/10000 N/C. calculate the time of travel

Q. In a photo emissive cell, with exciting wavelength $\lambda$, the maximum kinetic energy of electron is $K$. If the exciting wavelength is changed to$\frac{3\lambda }{4}$, the kinetic energy of the fastest emitted electron will be

1. $3K/4$
2. $4K/3$
3. less than $4K/3$
4. greater than $4K/3$

Q.

If E= hv, find the unit of h .

Q. The radius of a hydrogen atom in its ground state is $5.3\times {10}^{–11}\text{m}$. After collision with an electron, it is found to have a radius $21.2\times {10}^{–11}\text{m}.$ Find the value of $x$ where $x=6\times n$ and (where $n$ is principal quantum number) (integer only)

Q. According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is:

1. 
2. 
3. 
4. 

Q. What is piezo electric property?

Q.

When a potential difference (V) is applied across a conductor, the thermal speed of electrons is proportional to root of T . How ??

Q.

Figure (42-E2) is the plot of the stopping potential versus the frequency of the light used in an experiment on photoelectric effect. Find (a) the ratio h/e and (b) the work function.

Q. Which of the following figure represents the variation of particle's momentum and its associated de-Broglie wavelength

1. 
2. 
3. 
4. 

Q. If the frequency of light in a photoelectric experiment is doubled, the stopping potential will .

1. be doubled
2. be halved
3. be more than double
4. be less than double

Q. Hydrogen ${(}_1{H}^1),$ Deuterium ${(}_1{H}^2)$, singly ionised Helium ${(}_2{H}^4{)}^{+}$ and doubly ionised lithium ${(}_{3}L{i}^6{)}^{++}$ all have one electron around the nucleus. Consider an electron transition from $n=2$ to $n=1$. If the wave lengths of emitted radiation are ${\lambda }_1,{\lambda }_2,{\lambda }_3$ and ${\lambda }_4$ respectively then approximately which one of the following is correct ?

1. ${\lambda }_1=2{\lambda }_2=3{\lambda }_3=4{\lambda }_4$
2. ${\lambda }_1=2{\lambda }_2=2{\lambda }_3={\lambda }_4$
3. ${\lambda }_1={\lambda }_2=4{\lambda }_3=9{\lambda }_4$
4. $4{\lambda }_1=2{\lambda }_2=2{\lambda }_3={\lambda }_4$

Q. Light with energy flux of $18{\text{W/cm}}^2$ falls on a non-reflecting surface, of area $20{\text{cm}}^2$, at normal incidence. The momentum delivered in $30\text{minute}$ is -

1. $1.08\times {10}^{-5}{\text{kg-ms}}^{-1}$
2. $2.16\times {10}^{-3}{\text{kg-ms}}^{-1}$
3. $1.08\times {10}^{-3}{\text{kg-ms}}^{-1}$
4. $2.16\times {10}^{-5}{\text{kg-ms}}^{-1}$

Q.

In a photoelectric experiment, the potential difference $V$ that must be maintained between the illuminated surface and the collector so as just to prevent any electron from reaching the collector is determined for different frequencies $f$ of the incident illumination. The graph obtained is shown. The maximim kinetic energy of the electrons emitted at frequency $f_1$ is

1. $h{f}_1$
2. $h(f_1-f_0)$
3. $e{V}_1(f_1-f_0)$
4. $\frac{V_1}{(f_1-f_0)}$

Q. An unpolarized beam of light of intensity $I_0$ falls on a polaroid. The intensity of the emergent beam is,
$($Given average value of ${\cos }^2\theta =\frac{1}{2})$

1. $\frac{I_0}{2}$
2. $I_0$
3. $\frac{I_0}{4}$
4. zero

Q.

An electron in a hydrogen like atom is in an excited state. it has a total energy of $–3.4eV$. The de Broglie wavelength of the electron is nearly

Q. The slits in a Young's double slit experiment are illuminated by two different wavelengths ${\lambda }_1$ and ${\lambda }_2$. A thin film is placed in front of the slit $S_1$, which blocks ${\lambda }_1$ and allows ${\lambda }_2$ to pass. Another thin film is placed in front of $S_2$ such that it blocks ${\lambda }_2$ and allows ${\lambda }_1$ to pass. Then, on the screen, we will observe

1. an interference pattern due to both ${\lambda }_1$ and ${\lambda }_2$
2. an interference pattern due to ${\lambda }_1$ only, which is shifted along $S_1$
3. an interference pattern due to ${\lambda }_2$ only, which is shifted along $S_2$
4. no interference pattern

Q. In an experiment on photoelectric effect, the slope of the cut-off voltage versus frequency of incident light is found to be 4.12 × 10–15 V s. Calculate the value of Planck’s constant.

Q.

The work function of cesium metal is $2.14eV$. When the light of frequency $6\times {10}^{14}Hz$ is incident on the metal surface, photoemission of electrons occurs. What is the

1. the maximum kinetic energy of the emitted electrons
2. Stopping potential
3. the maximum speed of the emitted photoelectrons

Q.

What does Youngs experiment prove?

Q. A mercury lamp is a convenient source for studying frequency dependence of photoelectric emission, since it gives a number of spectral lines ranging from the UV to the red end of the visible spectrum. In our experiment with rubidium photo-cell, the following lines from a mercury source were used: λ1 = 3650 Å, λ2 = 4047 Å, λ3 = 4358 Å, λ4 = 5461 Å, λ5 = 6907 Å, The stopping voltages, respectively, were measured to be: V01 = 1.28 V, V02 = 0.95 V, V03 = 0.74 V, V04 = 0.16 V, V05 = 0 V Determine the value of Planck’s constant h, the threshold frequency and work function for the material. [Note: You will notice that to get h from the data, you will need to know e (which you can take to be 1.6 × 10–19 C). Experiments of this kind on Na, Li, K, etc. were performed by Millikan, who, using his own value of e (from the oil-drop experiment) confirmed Einstein’s photoelectric equation and at the same time gave an independent estimate of the value of h.]

Q.

The photoelectric threshold frequency of a material is $\nu$.When the light of frequency $4\nu$ is incident on the metal, the maximum kinetic energy of the emitted photoelectron is?

1. $3h\nu$

2. $4h\nu$

3. $5h\nu$

4. $6h\nu$

Q. 6. Two line A and B in the plot given below shows the variation of de- Broglie wavelength lambda vs \sqrt{}v , where v is the accelerating potential for two particles carrying same charge.Which one of the two represents a particle of smaller mass?

Q. The work function of cesium metal is 2.14 eV. when light of frequency $6\times {10}^{14}Hz$ is incident on the metal surface, photoemission of electron occurs. find the (i) energy of incident photons (ii) maximum kinetic energy of photoelectrons.

Q. Representing stopping potential V along y-axis and 1/λ along x-axis for a given photocathode of work function ω_{°. }The curve is a straight line , the intercept on x-axis is equal to 1) ω_°/hc 2)hc/ω_° 3)ω_° c/h 4)

Q.

Which of the following predictions of the classical wave model of light (Maxwell's EM theory) were contradicted by the observations during the photoelectric effect experiment?

1. Increasing the intensity will increase the photocurrent.

2. For a moderate to high intensity, there will be some photocurrent no matter what the frequency is.

3. Increasing intensity of light while keeping the frequency constant will result in a higher (more negative) stopping potential.

4. Keeping the intensity fixed, changing the frequency should not affect the stopping potential at all.

Q.

1. $\frac{h}{e}$
2. $eh$
3. $h$
4. $\frac{e}{h}$

Q. When a centimeter thick surface is illuminated with light of wavelength $\lambda$, the stopping potential is V. When the same surface is illuminated by light of wavelength $2\lambda$, the stopping potential is $\frac{V}{3}$. The threshold wavelength for the surface is

1. $\frac{4\lambda }{3}$
2. $4\lambda$
3. $6\lambda$
4. $\frac{8\lambda }{3}$

Q. Derive the relationshipof number of photons and frequency of two equally energetic beams of lights.if there are n1 of frequency v1 in first beam and n2 photons of frequency v2?

Q. When a metallic surface is illuminated with light of wavelength $\lambda$, the stopping potential is $X$ volt. When the same surface is illuminated by light of wavelength $2\lambda$, the stopping potential is $\frac{x}{3}$. Threshold wavelength for the metallic surface is:

1. $\frac{4\lambda }{3}$
2. $4\lambda$
3. $6\lambda$
4. $\frac{8\lambda }{3}$