Method of finding LCM

Q. A p-n photodiode is made of a material with a band gap of 2.0 eV. The minimum frequency of the radiation that canbe absorbed by the material is nearly. [AIPMT (Prelims)-2008] (1)20 1014 Hz (2)10 1014 Hz (3)5 1014 Hz (4)1 1014 Hz

Q. The maximum energy $K_{max}$ of photoelectrons emitted in a photoelectric cell is measured using lights of various frequencies $v$. The given graph shows how $K_{max}$ varies with $v$. The slope of the graph is equal to

1. the charge of an electron
2. the charge to mass ratio of an electron
3. the work function of the emitter in the cell
4. Planck's constant.

Q.

When stopping potential is applied in an experiment on photoelectric effect, no photocurrent is observed. This means that

1. The photoelectrons are emitted but are re-absorbed by the emitter metal

2. The emission of photoelectrons is stopped

3. The photoelectrons are dispersed from the sides of the apparatus.

4. The photoelectrons are accumulated near the collector plate

Q. Assuming photoemission to take place, the factor by which the maximum velocity of the emitted photoelectrons changes when the wavelength of the incident radiation is increased four times, is

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

Q.

What frequency can be measured by wein bridges?

Q.

In the Photoelectric setup, I would like to achieve stopping potential by making one of the plates in the setup, positively charged. Which one should I charge positively?

1. The collector plate

2. Stopping potential cannot be achieved by making any plate positively charged

3. More data is required to make a selection

4. The emitter plate

Q. Will making the collector plate positive affect the saturation current?

1. Yes
2. No

Q. The maximum kinetic energy of photoelectrons emitted from a surface when photons of energy 6 eV fall on it is 4 eV. the stopping potential in volts is

1. 2
2. 4
3. 6
4. 10

Q. When radiation is incident on a photo electron emitter, the stopping potential is found to be 9 V. If $\left(\frac{e}{m}\right)$ for the electron is $1.8\times {10}^{11}ck{g}^{-1}$, the maximum velocity of the ejected electron is

1. $6\times {10}^{5}m{s}^{-1}$
   
2. $8\times {10}^{5}m{s}^{-1}$
   
3. $1.8\times {10}^{6}m{s}^{-1}$
   
4. $0.8\times {10}^{3}m{s}^{-1}$
   

Q. Monochromatic light of frequency ${\nu }_1$ irradiates a photocell and the stopping potential is found to be $V_1$. What is the new stopping potential of the cell if it is irradiated by monochromatic light of frequency ${\nu }_2$?

1. $V_1+\frac{h}{e}({\nu }_2-{\nu }_1)$
2. $V_1-\frac{h}{e}({\nu }_2-{\nu }_1)$
3. $V_1-\frac{h}{e}({\nu }_1+{\nu }_2)$
4. $V_1+\frac{h}{e}({\nu }_1+{\nu }_2)$

Q. When a point source of light is at a distance of 50 cm from a photoelectric cell, the cut off voltage is found to be $V_0$. If the same source is placed at a distance of 1 m from the cell, the cut off voltage will be

1. $V_0$
2. $\frac{V_0}{4}$
3. $\frac{V_0}{2}$
4. $2V_0$

Q. A metal whose work function is $3.3eV$ is illuminated by light of wavelength $3\times {10}^{-7}$ m. What is the threshold frequency for photoelectric emission? Given Planck's constant $=6.6\times {10}^{-34}Js$.

1. $0.4\times {10}^{15}Hz$
2. $0.8\times {10}^{15}Hz$
3. $1.6\times {10}^{15}Hz$
4. $3.2\times {10}^{15}Hz$
   

Q. In a photo electric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is

1. 1.8 V
2. 1.3 V
3. 0.5 V
4. 2.3 V

Q.

According to the classical wave picture of light, how would the current versus potential (between the plates) graph vary upon varying intensity?

1. 

2. 

3. 

4. 

Q.

In a photo electric experiment 4 electrons with varying kinetic energy come out.

$E1=1.6\times {10}^{-19}JE2=2.1\times {10}^{-19}JE3=3.2\times {10}^{-19}JE1=1.2\times {10}^{-19}J$

The stopping potential , given this data will be __ Volt

Q. The linear momentum of an electron, initially at rest, accelerated through a potential difference of 100 V is (in kg $m{s}^{-1}$)

1. $2.25\times {10}^7$
2. $5.4\times {10}^{-24}$
3. $5.4\times {10}^7$
4. $2.85\times {10}^{-24}$

Q. If the radius of the dees of the cyclotron ir r, then the kinetic energy of a proton of mass m accelerated by the cyclotron at an oscillating frequency will be

Q.

In Photoelectric setup as soon as the potential reaches $V_o$ (stopping potential), the electrons stop coming out of the emitter plate.

1. True

2. False