The Photon Model

Q.

Photons of energy 6 eV are incident on a metal surface whose work function is 4 eV. The minimum kinetic energy of the emitted photo-electrons will be

Q.

Two identical capacitors each of capacitance $5\mu F$ are charged to potential $2KV$ and $1KV$ respectively. There negative ends are connected together, when the positive ends are also connected together, the loss of the energy of the system is.

Q. When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however light of 600 nm wavelength is sufficient for creating photoemission. What is the ratio of the work functions of the two emitters

1. 1 : 2
2. 2 : 1
3. 1 : 4
4. 4 : 1

Q. What is the stopping potential for photoelectrons ejected from a photosensitive material of work function 1.6 eV when it is irradiated by photons of energy 2.4 eV?

1. 2.0 V
2. 0.8 V
3. 4.0 V
4. None of these

Q.

A tube light of 40 W runs at 220 V. What is the current in the tube light and how much energy in kWh it will consume in 10 hours?

Q. A photon of energy 3.4 eV is incident on a metal having work function 2 eV. The maximum K.E. of photo-electrons is equal to

1. 1.4 eV
2. 6.8 eV
3. 5.4 eV
4. 1.7 eV

Q.

If threshold wavelength for sodium is $6800\stackrel{\circ }{A}$ then the work function will be

1. 1.8 eV

2. 2.1 eV

3. 2.5 eV

4. 1.4 eV

Q.

The work function of a metal is 4.2 eV, its threshold wavelength will be

1. $4000\stackrel{\circ }{A}$

2. $2500\stackrel{\circ }{A}$

3. $3500\stackrel{\circ }{A}$

4. $2955\stackrel{\circ }{A}$

Q.

Define the threshold wavelength in the photoelectric effect.

Q. When a metallic surface is illuminated by a light of wavelength $\lambda$ the stopping potential for the photoelectric current is 3 V. When the same surface is illuminated by light of wavelength $2\lambda$ the stopping potential is 1 V. The threshold wavelength of this surface is

1. $\lambda$
2. $3\lambda$
3. $4\lambda$
4. $2\lambda$

Q.

The cathode of a photoelectric cell is changed such that the work function changes from $W_{1}to{W}_2(W_2>W_1)$. If the current before and after change are $l_{1}and{l}_2$ all other conditions remaining unchanged, then (assuming hn > $W_2$)

1. $I_1=I_2$

2. $I_1>I_2$

3. $I_1<I_2<2I_1$

4. $I_1<I_2$

Q.

Energy of photon whose frequency is ${10}^{12}MHz$, will be

1. $4.14\times {10}^{2}eV$

2. $4.14\times {10}^{3}MeV$

3. $4.14\times {10}^{3}KeV$

4. $4.14\times {10}^{3}eV$

Q. Light from a hydrogen discharge tube is incident on the cathode of a photoelectric cell. The work function of the cathode surface is 4.2 eV. In order to reduce the photo-current to zero the voltage of the anode relative to the cathode must be made

1. – 4.2 V
2. – 9.4 V
3. – 17.8 V
4. +9.4 V

Q.

In the formula, $\mathrm{E}=\mathrm{hv}$, $E$ is ___ and $v$ is ___.

Q. For a photo electric experiment the relation between applied potential difference between cathode and anode (V) and the photo electric current (I) was found be as shown in fig. What is the frequency of incident radiation would be nearly $(h=6.6\times {10}^{-34}Js)$

1. $0.436\times {10}^{18}Hz$
2. $0.775\times {10}^{15}Hz$
3. $0.421\times {10}^{25}Hz$
4. $0.821\times {10}^{23}Hz$

Q. An electron jumps from n = 4 to n = 1 state in H-atom. The recoil momentum of H-atom (in eV/C) is

1. 12.75
2. 0.85
3. 6.75
4. 14.45

Q. Photon A has twice the energy of photon B. Then which option is correct?

1. Momentum of A is less than momentum of B.
2. Wavelength of A is less than wavelength of B.
3. Wavelength of A is equal to wavelength of B.
4. Wavelength of A is greater than wavelength of B.

Q. Work function of lithium and copper are respectively 2.3 eV and 4.0 eV. Which one of the metal will be useful for the photoelectric cell working with visible light ? $(h=6.6\times {10}^{-34}J-s,c=3\times {10}^{8}m/s)$

1. Lithium
2. Copper
3. None of them can be used
4. Both

Q.

If the work function of a metal is ${}^{\prime }{\varphi }^{\prime }$ and the frequency of the incident light is 'v', there is no emission of photoelectron if

1. $v<\frac{\varphi }{h}$

2. $v=\frac{\varphi }{h}$

3. $v>\frac{\varphi }{h}$

4. $v>=<\frac{\varphi }{h}$

Q.

The photo-electrons emitted from a surface of sodium metal are such that

1. They all are of the same frequency

2. They have the same kinetic energy

3. They have the same de Broglie wavelength

4. They have their speeds varying from zero to a certain maximum

Q.

Mercury violet light $(\lambda =4558\stackrel{\circ }{A})$ is falling on a photosensitive material $(\varphi =2.5eV)$. The speed of the ejected electrons is in $m{s}^{-1}$, about

1. $3\times {10}^5$

2. $3.65\times {10}^7$

3. $2.65\times {10}^5$

4. $4\times {10}^4$

Q.

Light of frequency $4v_0$ is incident on the metal of the threshold frequency $v_0$. The maximum kinetic energy of the emitted photoelectrons is

1. $3h{v}_0$

2. $2h{v}_0$

3. $\frac{3}{2}h{v}_0$

4. $\frac{1}{2}h{v}_0$

Q.

The energy in monochromatic X-rays of wavelength 1 angstrom is roughly equal to

1. $2\times {10}^{-15}J$

2. $2\times {10}^{-16}J$

3. $2\times {10}^{-17}J$

4. $2\times {10}^{18}J$

Q.

When wavelength of incident photon is decreased then

1. Velocity of emitted photo-electron decreases

2. Photo electric current increases

3. Velocity of emitted photoelectron increases

4. Velocity of photoelectron do not charge

Q.

A hydrogen atom moving at a speed v absorbs a photon of wavelength 122 nm and stops. Find the value of v. Mass of a hydrogen atom $=1.67\times {10}^{-27}$ kg.

1. 3.25 m/s

2. 5.48 m/s

3. 9.8 m/s

4. 0.16 m/s.

Q.

The threshold wavelength for photoelectric effect of a metal is $6500\stackrel{\circ }{A}$. The work function of the metal is approximately

1. 2 eV

2. 1 eV

3. 3 eV

4. 0.1eV

Q. When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however light of 600 nm wavelength is sufficient for creating photoemission. What is the ratio of the work functions of the two emitters

1. 1 : 2
2. 2 : 1
3. 4 : 1
4. 1 : 4

Q.

If the work function of a photometal is 6.825 eV. Its threshold wavelength will be $(c=3\times {10}^{8}m/s)$

1. $1200\stackrel{\circ }{A}$

2. $1800\stackrel{\circ }{A}$

3. $2400\stackrel{\circ }{A}$

4. $3600\stackrel{\circ }{A}$

Q.

Photons with energy $5eV$ are incident on a cathode $C$ in a photoelectric cell. The maximum energy of emitted photoelectrons is $2eV$. When photons of energy $6eV$ are incident on $C$, no photoelectrons will reach the anode $A$, if the stopping potential of $A$ relative to $C$ is:

1. $-3V$

2. $+3V$

3. $+4V$

4. $-1V$

Q. The spectrum of radiation $1.0\times {10}^{14}Hz$ is in the infrared region. The energy of one photon of this in joules will be

1. $\frac{6.62}{3}\times {10}^{-28}$
2. $3\times 6.62\times {10}^{-28}$
3. $6.62\times {10}^{-48}$
4. $6.62\times {10}^{-20}$