Saturation Current

Q. Photoelectric emission is observed from a metallic surface for frequencies $v_1$ and $v_2$ of the incident light rays $\left(v_1\right)$ > $\left(v_2\right)$. If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of 1 : k, then the threshold frequency of the metallic surface is

1. $\frac{v_1-v_2}{k-1}$
2. $\frac{k{v}_2-v_1}{k-1}$
3. $\frac{k{v}_1-v_2}{k-1}$
4. $\frac{k{v}_2-v_1}{k-1}$

Q. 98. A: if an electron and proton possessing same kinetic energy enter an electric field in a perpendicular direction, the path of the electron is more curved than that of the proton R: electron forms a larger curve due to its small mass

Q.

Suppose that the particle in Exercise in 1.33 is an electron projected with velocity v_x= 2.0 × 10⁶ m s⁻¹. If E between the plates separated by 0.5 cm is 9.1 × 10² N/C, where will the electron strike the upper plate? (| e | =1.6 × 10⁻¹⁹ C, m_e = 9.1 × 10⁻³¹ kg.)

Q. The current voltage relation of diode is given by $I=(e^{\frac{1000V}{T}}–1)\text{mA}$, where the applied voltage $V$ is in volts and the temperature $T$ is in degree Kelvin. If a student makes an error of $\pm 0.01\text{V}$ while measuring the current of $5\text{mA}$ at $300\text{K}$, what will be the error in the value of current in $\text{mA}$?

Q.

A photon of energy hv is absorbed by a free electron of a metal having work function $\varphi <hv$

1. The electron is sure to come out with a kinetic energy hv – φ.

2. Either the electron does not come out or it comes out with a kinetic energy hv – φ.

3. The electron is sure to come out

4. It may come out with a kinetic energy less than hv – φ.

Q. The magnitude of saturation photoelectric current depends upon

1. Frequency
2. Stopping potential
3. Work function
4. Intensity

Q. In a certain region electric potential varies according to the relation V =xy - x2. The magnitude of electric field at (4, 5, 3) is

Q. An electron enters in higher potential V2 from lower potential V1, then its velocity (1)will increase (2)will change in direction but not in magnitude (3)will not change in direction of field

Q. The graph shows variation of stopping potential $V_0$ versus frequency of incident radiation v for two photosensitive metals A and B. Which of the two metals has higher threshold frequency and why?

Q. When a point source of light is at a distance of one meter from a photo cell, the cut off voltage is found to be $V$. If the same source is placed at $2\text{m}$ distance from photo cell, the cut off voltage will be -

1. $V$
2. $\frac{V}{2}$
3. $\frac{V}{4}$
4. $\frac{V}{\sqrt{2}}$

Q. In photoelectric effect the electrons are ejected from metals if the incident light has a certain maximum?

Q. when M radiations of frequencies 4\ast10^{15} Hz and 6\ast10^{15} Hz fall on the same metal in different experiments, the ratio of maximum kinetic energy of electrons liberated is 1:3.The threshold frequency for the metal is?

Q.

Which colour has the maximum stopping potential?

Q.

The current through the ideal diode as shown in the figure is:

1. 0A

2. 0.02A

3. 0.04A

4. 0.06A

Q.

A $2V$ battery is connected across the points A and B as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to A is

1. $0.2A$
2. $0.4A$
3. $0A$
4. $0.1A$

Q.

A point source of light is used in an experiment on photoelectric effect. Which of the following curves best represents the variation of photo current $\left(i\right)$ with distance $\left(d\right)$ of the source from the emitter

1. $c$
2. $d$
3. $a$
4. $b$

Q.

The voltage applied across an X-rays tube is nearly

1. 10 V

2. 100 V

3. 10000 V

4. 1000000V

Q.

Answer the following questions:

(a) A steady current flows in a metallic conductor of non-uniform cross- section. Which of these quantities is constant along the conductor: current, current density, electric field, drift speed?

(b) Is Ohm’s law universally applicable for all conducting elements?

If not, give examples of elements which do not obey Ohm’s law.

(c) A low voltage supply from which one needs high currents must have very low internal resistance. Why?

(d) A high tension (HT) supply of, say, 6 kV must have a very large internal resistance. Why?

Q. Find the maximum velocity of photoelectrons emitted by radiation of frequency 3 × 1015 H from a photoelectric surface having work function of 4.0 eV. \lbrack h = 6.6 × 10–34 J-s and me = 9.1 × 10–31 kg\rbrack

Q. A light source of frequency $v$ illuminates a metallic surface and ejects photoelectrons. The photoelectrons having maximum energy are just able to excite the hydrogen atom in ground state. When the whole experiment is repeated with an incident radiation of frequency $\frac{6}{5}v$, the photoelectrons so emitted are able to excite the hydrogen atom which then emit a radiation of six different wavelengths.

1. The work function of the metal is $3.15\text{eV}$
2. The work function of the metal is $2.55\text{eV}$
3. The frequency of radiation is $3.08\times {10}^{15}\text{Hz}$
4. The frequency of radiation is $3.08\times {10}^{14}\text{Hz}$

Q.

A potential difference created between the two plates in the photoelectric experiment setup helps to accelerate the photoelectrons, so that all of them reach the collector plate and contribute to the current. In the absence of such an accelerating potential, will there be any photocurrent at all? (Assume the photoelectrons come out perpendicular to the emitter plate.)

1. Yes, as long as hv > φ

2. No, there needs to be a pull from the collector plate for current to exist, just like any battery driven circuit

3. Yes, but only if the intensity of light is extremely high

4. Yes, but only if the frequency of light v is extremely high

Q. The kinetic energy of the photoelectrons ejected from the metal surface $A$ is $K$ when required radiation is incident. If the same radiation is capable of ejecting the electrons from the metal $B$ with higher work function, then the kinetic energy of the photoelectrons -

1. $=K$
2. $>K$
3. $<K$
4. $\ge K$

Q. When photons of energy hv fall on an aluminium plate (of work function Eo), photoelectrons on maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be (1) K + Eo (2) 2K (3) K (4) K + hv

Q. An electron of energy 150 eV has wavelength of 10^{-10} m. The wavelength of a 0.60 keV electron is (a) 0.50 A^{†extdegree }(b) 0.75 A^{†extdegree }(c) 1.2 A^{†extdegree }(d) 1.5 A^†extdegree.

Q. The Current voltage relation of diode is given by $I=(e^{1000V/T}-1)\text{mA}$, where the applied voltage $V$ is in volts and the temperature $T$ is in degree Kelvin. If a student makes an error measuring $\pm 0.01\text{V}$ while measuring the current of $5\text{mA}$ at $300\text{K}$, what will be the error in the value of current in $\text{mA}$ ?

1. $0.05\text{mA}$
2. $0.02\text{mA}$
3. $0.2\text{mA}$
4. $0.5\text{mA}$

Q. 1.What is the net flux through a prism in which charge is kept at the corner and angle is 45^°

Q. If a metal sheet is irradiated with radiations of frequency n1 and n2 and kinetic energy of photoelectrons is in the ratio of 1:x then threshold frequency of metal is:

Q. If the kinetic energy of the particleis increased to 16 times its previous value the percentage change in the debroglie wavelength of the particle is

Q. A deuteron of kinetic energy 50 KeV is describing a circular orbit of radius 0.5 metre in a plane perpendicular to the magnetic field B . The kinetic energy of the proton that describes a circular orbit of radius 0.5 metre on the same plane with the same B is .?

Q. Photoelectric work function of a metal is 1 ev.light of wavelength 3000A^° falls on it. What is the velocity of the ejected photoelectron.