Photoelectric Effect

Q.

What is the failure of classical mechanics?

Q. The number of photoelectrons emitted depends upon:

1. The intensity of the incident radiation
2. The frequency of the incident radiation
3. The product of intensity and frequency of the incident radiation
4. None of these

Q. The given diagram indicates the energy level of a certain atom. When an electron moves from 2E level to E level, a photon of wavelength $\lambda$ is emitted. The wavelength of photon emitted during its transition from $\frac{4E}{3}$ level to E level is:
____ $2E$
____$\frac{4E}{3}$
____ $E$

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

Q.

If $150J$of energy is incident on the area$2m^2$. If $Q_r=15J$, the coefficient of absorption is $0.6,$ then the amount of energy transmitted is

1. $50J$

2. $45J$

3. $40J$

4. $30J$

Q.

If the work function of a metal is $3.7eV$. When a photon of energy $5.2eV$ falls on the metal surface then the kinetic energy of ejected photoelectrons will be ______.

Q.

A bulb emits light of wavelength $\lambda =4500A˚$. The bulb is rated as $150watt$ and $8\%$ of the energy is emitted as light. How many photons are emitted by the bulb per second?

Q.

A sodium incandescent bulb emits $589nm$ wavelength light at $60watts$. calculate the number of photons emitted by the bulb.

Q. In photoelectric effect, the kinetic energy of photoelectrons increases linearly with the

1. Wavelength of incident light
2. Frequency of incident light
3. Velocity of incident light
4. Atomic mass of an element.

Q.

What are the postulates of max plank?

Q.

When a certain metal was irradiated using a light of frequency $8.1\times {10}^{16}$ Hz the photoelectron emitted had 1.5 times the kinetic energy as did the photoelectrons emitted when the same metal was irradiated using a light of frequency $5.8\times {10}^{16}$ Hz. If the same metal is irradiated using light of wavelength 3.846 nm, what will be the kinetic energy of the photoelectron emitted?

1. 180 eV
2. $3.65\times {10}^{-17}$ J
3. $2.28\times {10}^2$ eV
4. $4.37\times {10}^{-17}$ J

Q. The ejection of photoelectrons from a silver metal sample in the photoelectric effect experiment can be stopped by applying a voltage of 0.35 eV with a radiation of 256.7 nm. Calculate the work function for the silver metal sample.

1. 4.48 eV
2. 2.48 J
3. 4.48 J
4. 2.48 eV

Q. If we plot a graph of stopping potential of photoelectrons against the frequency (in hertz) of radiation that has emitted, then its slope would be:
($h=6.6\times {10}^{-34})$

1. 6.625 $\times {10}^{-34}$
2. 0.414 $\times {10}^{-14}$
3. 3.656 $\times {10}^{12}$
4. 5.796 $\times {10}^{18}$

Q.

What did Einstein say about the photoelectric effect?

Q. Which of the following graph is correct between maximum kinetic energy vs frequency plotted for three different materials photo-emissions?

1. 
2. 
3. 
   
4. 

Q. When electromagnetic radiation of wavelength $300nm$ falls on the surface of sodium, electrons are emitted with a kinetic energy of $1.68\times {10}^{5}Jmo{l}^{-1}$. What is the maximum wavelength that will cause a photoelectron to be emitted?

1. $\lambda =320nm$
2. $\lambda =449.7nm$
3. $\lambda =526nm$
4. $\lambda =518nm$

Q. If a radiation of wavelength $470\text{nm}$ falls on the surface of potassium metal, eletcrons are emitted with a maximum velocity of $6.4\times {10}^4{\text{m s}}^{-1}$.
Stopping potential of the given circuit is:

1. 1.21 V
2. 0.131 V
3. 1.16 V
4. 0.116 V

Q. When radiation of $\lambda =253.7\text{nm}$ strikes the copper plate, the energy required to stop the ejection of electrons from copper plate is $0.24\text{eV}$. Calculate the work function of copper.

1. $4.64\text{eV}$
2. $6.65\text{eV}$
3. $8.45\text{eV}$
4. $10.25\text{eV}$

Q.
The work function of metals is listed below. The number of metals which will show photoelectric effect when light of 300 nm wavelength falls on the metal is:

Metal	Li	Na	K	Mg	Cu	Ag	Fe	Pt	W
$\varphi$ eV	2.4	2.3	2.2	3.7	4.8	4.3	4.7	6.3	4.75

1. 
   4
2. 
   6
3. 
   5
4. 
   9

Q. The number of photoelectrons emitted depends upon:

1. The intensity of the incident radiation
2. The frequency of the incident radiation
3. The product of intensity and frequency of the incident radiation
4. None of these

Q. Radiation of wavelength $3000\stackrel{o}{A}$ falls on a photoelectric surface for which work function is 1.6 eV. What is the stopping potential for emitted electron

1. 2.53 V
2. 3.32 V
3. 1.20 V
4. 5.20 V

Q.

A photon of 300 nm is absorbed by a gas, which then re-emits two photons. One re-emitted photon has a wavelength of 400 nm. Calculate the energy of the other photon re-emitted out.

1. $16.56\times {10}^{-18}J$

2. $16.56\times {10}^{-12}J$

3. $16.56\times {10}^{-20}J$

4. $16.56\times {10}^{-15}J$

Q.
The threshold frequency of a metal is $6\times {10}^{14}{s}^{-1}$. Calculate the kinetic energy of an electron emitted when radiation of frequency $1.1\times {10}^{15}{s}^{-1}$ hits the metal.

1. $3.31\times {10}^{-19}$ J
2. $1.13\times {10}^{-18}$ J
3. $7.12\times {10}^{-19}$ J
4. None of These

Q. Which out of the following can explain the photoelectric emission?

1. Wave nature of light
2. Particle nature of light
3. Dual nature of light
4. None of this

Q. The work function of $Pt$ is twice as the work function of $Ca$. If the minimum photon energy required to emit photoelectrons from the surface of $Pt$ is $E$, then that for the surface of $Ca$ would be:

1. $2E$
2. $1.5E$
3. $0.5E$
4. Cannot be determined

Q. When radiation of certain wavelength shines on the cathode of the photoelectric cell, the photocurrent produced can be reduced to zero by applying stopping potential of 3 V. If the workfunction of the photo emitter is 3.63 eV, find the frequency of radiation

1. $3.2\times {10}^{15}$ Hz
2. $1.6\times {10}^{15}$ Hz
3. $1.6\times {10}^{12}$ Hz
4. $3.2\times {10}^{12}$ Hz

Q. The work function of metal is $4\text{eV}$. To emit a photo electron of zero velocity from the surface of metal, the wavelength of incident light should be:

1. $2700\stackrel{o}{\text{A}}$
2. $1700\stackrel{o}{\text{A}}$
3. $5900\stackrel{o}{\text{A}}$
4. $3100\stackrel{o}{\text{A}}$

Q. A certain metal was irradiated with light of frequency $3.2\times {10}^{16}$ Hz. The photoelectrons emitted had twice the kinetic energy as did photoelectrons emitted when the same metal was irradiated with light of frequency $2\times {10}^{16}$Hz. Calculate the threshold frequency for the metal.

1. $8\times {10}^{15}Hz$
2. $6\times {10}^{15}Hz$
3. $8\times {10}^{12}Hz$
4. $6\times {10}^{12}Hz$

Q. If wavelength of $470\text{nm}$ falls on the surface of potassium metals, eletcrons are emitted with a velocity of $6.4\times {10}^5{\text{m s}}^{-1}$.
The work function of potassium metal is:

1. $2.36\times {10}^{-19}\text{J}$
2. $1.86\times {10}^{-21}\text{J}$
3. $4.25\times {10}^{-30}\text{J}$
4. $4.2\times {10}^{-18}\text{J}$

Q. The mass of an electron is $9.1\times {10}^{-31}kg$. If the K.E. is given as $3.0\times {10}^{-25}J$. Calculate the wavelength of the electron.

1. $8967\stackrel{o}{A}$
2. $6242\stackrel{o}{A}$
3. $7264\stackrel{o}{A}$
4. $6966\stackrel{o}{A}$

Q. A radiation of energy $E(E>E_0)$ falls on a metal whose threshold frequency is $E_0$. The Kinetic energy of the emitted electrons is given by:

1. $\frac{E-E_o}{2}$
2. $E-E_o$
3. $E_o-E$
4. $\frac{E}{E_o}$