## DUAL NATURE OF RADIATION AND MATTER quiz-16

As per analysis for previous years, it has been observed that students preparing for NEET find Physics out of all the sections to be complex to handle and the majority of them are not able to comprehend the reason behind it. This problem arises especially because these aspirants appearing for the examination are more inclined to have a keen interest in Biology due to their medical background. Furthermore, sections such as Physics are dominantly based on theories, laws, numerical in comparison to a section of Biology which is more of fact-based, life sciences, and includes substantial explanations. By using the table given below, you easily and directly access to the topics and respective links of MCQs. Moreover, to make learning smooth and efficient, all the questions come with their supportive solutions to make utilization of time even more productive. Students will be covered for all their studies as the topics are available from basics to even the most advanced. .

Q1. A charged oil drop of mass 2.5×10-7 kg is in space between the two plates, each of area 2×10-2 m2 of a parallel plate capacitor.
When the upper plate has a charge of 5×10-7 C and the lower plate has an equal negative charge, the oil remains stationary. The charge of the oil drop is [Take g=10 m/s2]
•  9×10-1 C
•  9×10-6 C
•  8.85×10-13 C
•  1.8×10-14 C
Solution
We know that qE=mg qQ/(ε0 A)=mg or q=(ε0 Amg)/Q =(8.85×10-12×2×10-2×2.5×10-7×10)/(5×10-7 ) C =8.85×10-13 C

Q2.Light of wavelength 4000Åis incident on a metal surface. The maximum kinetic energy of emitted photoelectron is 2 eV. What is the work function of the metal surface ?
•  4 eV
•  1 eV
•  2 eV
•  6 eV
Solution
According to Einstein’s photoelectric equation the work function of metal is given by ∴ ϕ= hc/λ-KEm = (6.6×10-34×3×108)/(4000×10-10 )-2eV = 4.95×10-19-2 eV = (4.95×10-19)/(1.6×10-19 )-2 eV = 3 eV-2 eV = 1 eV

Q3. If λ1 and λ2 are the wavelengths of characteristic X-rays and gamma rays respectively, then the relation between them is
•  λ1=1/λ2
•  λ12
•  λ12
•  λ12
Solution
In general X-rays have larger wavelength than that of gamma rays

Q4. Who discovered the charge on an electron for the first time?
•  Millikan
•  Thomson
•  Kelvin
•  Coulomb
Solution
Millikan

Q5.The wavelength of the photoelectric threshold for silver is λ0. The energy of the electron ejected from the surface of silver by an incident light of wavelength λ(λ<λ0) will be
•  hc(λ0-λ)
•  hc/(λ0-λ)
•  h/c (1/λ-1/λ0 )
•  hc(λ0- λ)/(λ0 λ)
Solution
Ek=hc/λ-hc/λ0 =hc[(λ0-λ)/(λ0 λ)]

Q6. When light falls on a metal surface, the maximum kinetic energy of the emitted photo-electrons depends upon
•  The time for which light falls on the metal
•  Frequency of the incident light
•  Intensity of the incident light
•  Velocity of the incident light
Solution
Kmax=(hv-W0 );v= frequency of incident light

Q7.In X-ray experiment Kα,Kβ denotes
•  Characteristic
•  Continuous wavelength
•  α,β-emissions respectively
•  None of these
Solution
Characteristic

Q8. Light of wavelength 4000 Å falls on a photosensitive metal and a negative 2V potential stops the emitted electrons. The work function of the material (in eV) is approximately (h=6.6×10-34 Js,e=1.6×10-19 C,c=3×108 ms-1)
•  1.1
•  2.0
•  2.2
•  3.1
Solution
Energy of incident light E(eV)=12375/4000=3.09 eV Stopping potential is -2V so Kmax=2 eV Hence by using E=W0+Kmax;W0=1.09 eV=1.1 eV

Q9.An α-particle of mass 6.4×10-27kg and charge 3.2×10-19 C is situated in a uniform electric field of 1.6×105 Vm-1. The velocity of the particle at the end of 2×10-2 m path when it starts from rest is
•  2√3×105 ms-1
•  8×105 ms-1
•  16×105 ms-1
•  4√2×105 ms-1
Solution
Given, m_α=6.4×10-27)kg qα=3.2×10-19 C, E=1.6×105 Vm-1 Force on α-particle F=qα F=3.2×10-19×1.6×105 =51.2×10-15N Now, acceleration of the particle α=F/mα =(51.2×10-15)/(6.4×10-27 )=0.8×1013 ms-2 ∵Initial velocity, u=0 ∴ v2=2αs =2×8×1012×2×10-2=32×1010 or v=4√2×105 ms-1

Q10. When ultraviolet rays are incident on metal plate, then photoelectric effect does not occur. It occurs by the incidence of
•  X-rays
•  Infrared rays
•  Green house effect
Solution
λ(X-ray)(UV-ray) ## Want to know more

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QUIZ-16 DUAL NATURE OF RADIATION AND MATTER