Dual Nature of Radiation and Matter

Dual Nature of Radiation and Matter Class 12 MCQs Questions with Answers

Question 1.
Photoelectrons are being obtained by irradiating zinc by a radiation of 3100 Å. In order to increase the kinetic energy of ejected photoelectrons.
(a) the intensity of radiation should be increased.
(b) the wave length of radiation should be increased.
(c) the wavelength of radiation should be decreased.
(d) both wavelength and intesity of radiation should be increased.

Question 2.
The de-Broglie wavelength of an electron moving with a speed of 6.6 × 10¹⁵ ms^-1 is nearly equal to
(a) 10^-11m
(b) 10^-9 m
(c) 10^-7 m
(d) 10^-5 m

Question 3.
An electron accelerated through a potential difference of V volt has a wavelength λ associated with it, Mass of proton is nearly 2000 times that of an electron. In order to have the same λ for proton, it must be accelerated through a potential difference (in volt) of
(a) V
(b) \(\sqrt{2000}\) V
(c) 2000V V
(d) \(\frac{V}{2000}\)

Question 4.
An electron of mass m, when accelerated through a potential difference V, has de-Broglie wavelength λ. The de-Broglie wavelength associated with a proton of mass M and accelerated through the same potential difference will be
(a) λ\(\sqrt{\frac{m}{M}}\)
(b) λ\(\frac{m}{M}\)
(c) λ\(\sqrt{\frac{M}{m}}\)
(d) λ\(\sqrt{\frac{m}{m}}\)

Question 5.
The energy E and momentum p of a photon is given by E = hv h and p = \(\frac{h}{λ}\). The velocity of photon will be
(a) \(\frac{E}{P}\)
(b) (\(\frac{E}{P}\))²
(c) \(\sqrt{\frac{E}{P}}\)
(d) (EP)³

Question 6.
Ultra-violet radiation of 6.2 eV falls on an aluminium surface having work-function 4.2 eV. The kinetic energy (in J) of the fastest electron emitted is nearly.
(a) 3 × 10^-19
(b) 3 × 10^-15
(c) 3 × 10^-17
(d) 3 × 10^-21

Question 7.
For light of wavelength 5000 Å, the photon energy is nearly 2.5 eV. For X-rays of wavelength 1 Å, the photon energy will be close to:
(a) 2.5 × 5000 eV
(b) 2.5 ÷ 5000 eV
(c) 2.5 × (5000)² eV
(d) 2.5 ÷ (5000)² eV

Question 8.
A photocell is illuminated by a small bright source placed 1 metre away. When the same source of light is placed 2 m away, the electrons emitted per sec. (i.e. saturation current in the photo cell is) are
(a) I ∝ 2²
(b) I × \(\frac {1}{4}\)
(c) I ∝ 4
(d) I ∝ \(\frac {1}{2}\)

Question 9.
Which one of the following graph represent correctly the variation of maximum kinetic energy E_max with the intensity of incident radiations having a constant frequency.

Question 10.
The best metal to be used for photoemission is:
(a) Potassium
(b) Lithium
(c) Sodium
(d) Cesium

Question 11.
The threshold frequency for a certain metal is v₀. When light of frequency v = 2v₀ is incident on it, the maximum velocity of photo electrons is 4 × 10⁶ ms^-1. If the frequency of incident radiation is increased to 5 v₀, then the maximum velocity of photo electrons (m/s) is
(a) 8 × 10⁵
(b) 2 × 10⁶
(c) 2 × 10⁷
(d) 8 × 10⁶

Question 12.
The frequency and the intensity of a beam of light falling on the surface of photoelectric material are increased by a factor of two. This will:
(a) increase the maximum K.E. of photo-electron as well as photoelectric current by a factor of two.
(b) increase maximum K.E. of photoelectrons and would increase the photo current by a factor of two.
(c) increase the maximum K.E. of photo electrons by a factor of two and will no affect photoelectric current.
(d) No effect on both maximum K.E. and photoelectric current.

Question 13.
Which of the following is not the property of photons
(a) charge
(b) rest mass
(c) energy
(d) momentum

Question 14.
Dynamic mass of photon of wavelength k is
(a) Zero
(b) \(\frac {hc}{λ}\)
(c) \(\frac {h}{cλ}\)
(d) \(\frac {h}{2λ}\)

Question 15.
The time required in emitting photo electrons is
(a) 10^-8 s
(b) 10^-4 s
(c) Zero
(d) 1 sec

Question 16.
When light is directed at the metal surface, the emitted electrons:
(a) are called photons
(b) have energies that depend upon the intensity of light.
(c) have random energies.
(d) have energies that depend upon the frequency of light.

Question 17.
The wavelength associated with n electron is 1Å. The potential difference required for accelerating it is
(a) 100 V
(b) 150 V
(c) 250 V
(d) 10³ V

Question 18.
The momentum of a photon is 10^-27 kg ms^-1. Its energy will be:
(a) 3 × 10^-19 J
(b) 3 × 10^-34 j
(c) 3 × 10^-27 J
(d) none of these

Question 19.
With which of the following particles moving with same velocity de-Broglie wave length will be maximum?
(a) ß-particle
(b) ∝ particle
(c) electron
(d) proton

Question 20.
The magnification produced by electron microscope is of the order of:
(a) 10
(b) 10⁵
(c) 10³
(d) 10⁷

Question 21.
De-Broglie equation states the:
(a) dual nature
(b) particle nature
(c) wave nature
(d) none of these

Question 22.
Protons and alpha particles have the same de-Broglie wavelength. What is same for both of them ?
(a) Energy
(b) Time period
(c) Frequency
(d) Momentum

Question 23.
Kinetic energy of emitted electrons depends upon :
(a) frequency
(b) intensity
(c) nature of atmosphere surrounding the electrons
(d) none of these

Question 24.
De-Broglie wavelength of a body of mass m and kinetic energy E is given by (symbols have their usual meanings):
(a) \(\frac{h}{\sqrt{2mE}}\)
(b) \(\frac{h}{2mE}\)
(c) \(\frac{\sqrt{2mE}}{h}\)
(d) \(\frac{h}{mE}\)

Question 25.
The ratio of specific charge of an alpha particle to the proton is:
(a) 1 : 2
(b) 2 : 1
(c) 4 : 1
(d) 1 : 4

Question 26.
In Thomson’s experiment number of parabola gives :
(a) the no. of electrons present in element
(b) the no. of proton present in element
(c) the no. of neutrons present in element
(d) the no. of isotopes of the element present

Question 27.
The work function of photoelectric material is 3.3 eV. The threshold frequency will be equal to:
(a) 8 × 10¹⁴ Hz
(b) 8 × 10¹⁰ Hz
(c) 5 × 10¹⁰ Hz
(d) 4 × 10¹⁴ Hz

Question 28.
The strength of photoelectric current depends upon :
(a) angle of incident radiation
(b) frequency of incident radiation
(c) intensity of incident radiation
(d) distance between anode and cathode

Question 29.
The momentum of an electron that emits a wavelength of 2 Å. will be:
(a) 6.4 × 10^-36 kgms^-1
(b) 3.3 × 10^-24 kgms^-1
(c) 3.3 × 10^-34 kgms^-1
(d) none of these

Question 30.
Name the scientists who first studied the passage of electricity through fluids to establish the electrical nature of matter:
(a)Millikan
(b) Planck
(c) Faraday
(d) Boyle

Question 31.
Millikan’s oil drop experiment makes use of:
(a) Stokes’ law
(b) Boyle’s law
(c) Gas equation
(d) Bernoulli’s theorem

Question 32.
X-rays are:
(a) deflected by an electric field
(b) deflected by a magnetic field
(c) deflected by both electric and magnetic fields
(d) not deflected by electric and magnetic fields

Question 33.
In photo electric emission, for alkali metals the threshold frequency lies in the:
(a) visible region
(b) ultraviolet region
(c) infrared region
(d) far end of the infrared region

Question 34.
Which of the following radiations cannot eject photo electrons?
(a) ultraviolet
(b) infrared
(c) visible
(d) X-rays

Question 35.
What is the de-Broglie wavelength of an electron accelerated from rest through a potential difference of V volts?
(a) \(\frac{12.3}{V^2}\) Å
(b) \(\frac{12.3}{V}\) Å
(c) \(\frac{12.2}{V^2}\) Å
(d) None of these

Question 36.
What is the de-Broglie wavelength of an electron accelerated from rest through a potential difference of 100 volts?
(a) 12.3 Å
(b) 1.23 Å
(c) 0.123 Å
(d) None of these

Question 37.
What is the de-Broglie wavelength of a proton accelerated from rest through a potential difference of V volts?
(a) \(\frac{12.3}{√V}\) Å
(b) \(\frac{12.3}{V}\) Å
(c) \(\frac{12.2}{V^2}\) Å
(d) None of these

Question 38.
When a yellow light is incident on a surface, no electrons are emitted while green light can emit electrons. If the red light is incident on the surface then:
(a) no electrons are emitted
(b) photons are emitted
(c) electrons of higher energy are emitted
(d) electrons of lower energy are emitted

Question 39.
The de-Broglie wavelength of particle of mass 1 mg moving with a velocity of 1 ms^-1, in terms of Planck’s constant h, is given by (in metre):
(a) 10⁵ h
(b) 10⁶ h
(c) 10^-3 h
(d) 10³ h

Question 40.
Evidence of the wave nature of light cannot be obtained from:
(a) diffraction
(b) interference
(c) doppler effect
(d) reflection

Question 41.
which Characteristic of a target does the Mosley’s law relate the frequency of X-rays?
(a) density
(b) atomic number
(c) atomic weight
(d) interatomic space

Question 42.
The charge of a photo electron is :
(a) 9.1 × 10^-31 C
(b) 9.1 × 10^-27 C
(c) 9.1 × 10^-24 C
(d) none of these

Question 43.
The number of photons of frequency n present in energy E, in terms of Planck’s constant h:
(a) \(\frac{E}{nh}\)
(b) nhE
(c) \(\frac{nh}{E}\)
(d) \(\frac{nE}{h}\)

Question 44.
Compared to liquids and solids, gases are:
(a) good conductors of electricity
(b) best conductors of electricity
(c) very poor conductors of electricity
(d) good or bad conductors of electricity depending upon the nature of the gas

Question 45.
The different stages of discharge in a discharge tube can be explained on the basis of:
(a) the wave nature of light
(b) the dual nature of light
(c) wave nature of electrons
(d) the collision between the charged particles emitted from the cathode the atoms of the gas in the tube

Question 46.
When an electron jumps across a potential difference of 1 V, it gains energy equal to :
(a) 1.602 × 10^-19 J
(b) 1.602 × 10¹⁹ J
(c) 1.602 × 10²⁴ J
(d) 1 J

Fill in the Blanks

Question 1.
Stopping potential is the measure of the ………………… of the photoelectrons and does not depend upon …………………

Question 2.
In photoelectric effect experiment, photo electric current does not depend upon ………………… but depends only on the ………………… of incident reduction.

Question 3.
The threshold wavelength of a photo cathode to emit photoelectrons is λ₀. When a radiation of wavelength λ is incident on it, the average K.E. of the photoelectron is …………………

Question 4.
The stopping potential depends upon ………………… of incident light and ………………… of metal.

Question 5.
The maximum kinetic energy of emitted electrons in photoelectric effect is linearly dependent on the ………………… of the incident radiation.

Question 6.
The mass of a moving photon is …………………

Question 7.
The photoelectric threshold frequency of a metal is v₀. When light of frequency uv₀ is incident on the metal, the maximum kinetic energy of the emitted photoelectron is …………………

Question 8.
An electron beam passes at right angles to a magnetic field of 2 × 10^-3 Wb m^-2. The speed of the electron is 3 × 10⁷ ms^-1 An electric field of ………………… intensity should be applied along with the magnetic field so that the path of the electron beam remains indeviated.

Question 9.
An electron, photon, a neutron are accelerated through the same potential difference. The kinetic energies acquired by them will be in the ratio …………………

Question 10.
Light of frequency 1.5 times the threshold frequency is incident on a photo sensitive material. If the frequency of incident light is halved and the intensity is doubled, the photo current becomes …………………

Question 11.
A photon behaves as if it had a mass equal to ………………… and momentum equal to …………………

Question 12.
An electron is accelerated through a potential difference of 100 V. The wavelength associated with it is …………………

Question 13.
An electron is accelerated through a potential difference of 10⁴ V. The energy acquired by the electron is …………………

Question 14. Out of proton, neutron, ß-particle and a-particle ………………… will have the maximum de-Broglie wavelength.

Question 15.
If electrons photons are considered to be of same de- Broglie wavelength, then they will have the same …………………

Question 16.
If a photon and an electron ate considered to be of same de-Broglie wavelength, then the velocity of photon is …………………

Question 17.
An electron of mass m and charge e is accelerated from rest through a potential difference of V in vacuum. Its final velocity will be …………………

Question 18.
The mass of a photon at rest is …………………

Question 19.
When a proton is accelerated through a potential difference of one volt, the kinetic energy gained by it is roughly equal to …………………

Question 20.
Einstein’s photoelectric equation is expressed as …………………