Question bank Class 12 Physics Chapter14. Dual Nature Of Radiation And Matter.
Standard:- 12th
Question Bank
Subject:- Physics
Chapter14. Dual Nature Of Radiation And Matter.
MCQ’S (1 Mark Each)
1) The electrons are emitted in the photoelectric effect from a metal surface.
a) only if the frequency of radiation is above a certain threshold value.
b) only if the temperature of the surface is high .
c) at the that is independent of the nature of metal.
d) with a maximum velocity proportional to the frequency of incident radiation
Ans : a) only if the frequency of radiation is above a certain threshold value
2) As the intensity of incident light increases
a) photoelectric current increases
b) photoelectric current decreases.
c) kinetic energy of emitted photoelectrons increases
d) kinetic energy of emitted photoelectrons decreases.
Ans : a) photoelectric current increases.
3) The maximum kinetic energy of the photoelectrons depends only on
a) potential b) frequency c) incident angle d) pressure
Ans : b) frequency .
4) According to De-Broglie, the waves are associated with
a) moving neutral particles only.
b) moving charged particle only .
c) electrons only
d) all moving matter particles
Ans : d) all moving matter particles
5) The work function of a metal is 4.2 Ev.Its threshold wavelength will be
a) 4000 𝐴° b) 3500 𝐴° c) 2959 𝐴° d) 2500 𝐴°
Ans : c) 2959 𝐴° , 𝜆 =
∅°
6) Ultraviolet radiation of 6.2 eV falls on an aluminium surface (work function 4.2 eV). The kinetic energy in joules of the fastest electron emitted is
a) 3.2 × 10 b) 3.2 × 10 c) 3.2 × 10 d) 3.2 × 10
Ans : b) 3.2 × 10 ,𝐾. 𝐸 = h𝜈 −∅°
7) Plancks constant is 6.6 × 10 Js. The momentum of each photon in a given radiation
Is 3.3 × 10 kg/s. The λ of radiation is
a) 2 × 10 m b) 2 × 10 m c) 2 × 10 m d) 2 × 10m
Ans : d) 2 × 10 m , λ =
Very Short Answer (VSA) ( 1 MARK Each )
1 Define photoelectric effect .
2 Define threshold frequency.
3 What is cut off or stopping potential.
4 Define work function of the metal.
5 The minimum frequency for photoelectric effect on a metal is 7 × 10 Hz, Find the work function of the metal. Ans: ∅° = ℎ𝜈° = 4.62 × 10 J
6 Find the kinetic energy of emitted electron, if in a photoelectric effect energy of incident Photon is 4 eV and work function is 2.4 eV. Ans: 𝐾. 𝐸. =1.6 eV.
7 Find energy of photon which have momentum 2 × 10 gm-cm/sec.
Ans : E = 6 × 10 erg
Short Answer I (SA1) ( 2 MARKS Each )
1 Explain the term ‘wave particle duality’ of matter.
2 Draw a neat labelled diagram of schematic of experimental set up for photoelectric effect .
3 What is mean by dual nature of matter.
4 Explain the concept of photoelectric effect.
5 If the total energy of radiation of frequency 10Hz is 6.63 J , Calculate the number of photons in the radiation.
(Ans n= = 10)
6 An electron is accelerated through a potential of 120 V. Find its de Broglie wavelength.
( Ans:λ= . √ = 0.112 nm)
7 Calculate the stopping potential when the metal with the work function 0.6 eV is illuminated with the light of 2 eV. (Ans 𝑉 = ∅° = 1.4 V)
Short Answer II (SA2) ( 3 MARKS Each )
1) State Einstein photoelectric equation. Explain 2 characteristics of photoelectric effect on the basis of Einstein’s photoelectric equation.
2) With the help of circuit diagram describe an experiment to study photoelectric effect.
3) What is photoelectric effect? Define stopping potential and photoelectric work function.
4) Calculate De Broglie wavelength of bullet moving with speed 90m/sec and having a mass 5 gm.
(Ans λ = 1.472 x 10 m , λ = )
5) The energy of photon is 2 eV.Find its frequency and wavelength.
(Ans. Frequency, ν = = 4.826 x 10 Hz., Wavelengh 𝜆 =
= 6229 𝐴°)
6) The work function of a surface is 3.1 eV. A photon of frequency 1 x 10 Hz. Is incident on it. Calculate the incident wavelength is photoelectric emission occur or not.
(Ans 𝜆°=
∅°
= 4000 𝐴° photoelectric emission occur. )
Long Answer ( LA) ( 4 marks Each)
1) With the help of circuit diagram describe the experiment to study the characteristics of photoelectric effect,. Hence discuss any 2 characteristics of photoelectric effect.
2) State Einstein’s photoelectric equation . Explain all characteristics of photoelectric effect, on the basis of Einstein’s photoelectric equation.
3) Explain De Broglie’s Hypothesis.
