Case Study Questions Class 12 Physics Dual Nature of Radiation and Matter

Case Study Questions Class 12 Physics Chapter 11 Dual Nature of Radiation and Matter

CBSE Class 12 Case Study Questions Physics Dual Nature of Radiation and Matter. Term 2 Important Case Study Questions for Class 12 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Dual Nature of Radiation and Matter.

At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.

CBSE Case Study Questions Class 12 Physics Dual Nature of Radiation and Matter

Case study 1:

When a light of particular frequency is incident on the metal surface then there will be emission of photoelectrons takes place, such phenomenon is called as photoelectric effect. In this effect, when light of suitable frequency are incident on the metal surface then there will be collision between photons and free electrons of the metal takes place. The each free electron absorb the total energy hv of each photon and eject as a photoelectron from the metal surface with some sufficient kinetic energy. The minimum frequency of incident light above which photoelectrons are emitted from the metal surface is called as threshold frequency. And this threshold frequency depends on the nature of emitter plate used. Hence, it is different for different metals used. The electrons emitted from the metal during photoelectric effect are called as photoelectrons and the current constituted is called as photoelectric current. The number of photoelectrons emitted from the metal plate per second is directly proportional to the intensity of the incident radiation. More is the intensity more will be the photoelectric current. If the intensity of light incident may be large but if it is less than threshold frequency then there will be no emission of photoelectrons from the metal plate. The phenomenon of photoelectric effect is the instantaneous phenomenon. The phenomenon of photoelectric effect explains the particle nature of light. That means light waves are made up of quanta or packets of energy and each quanta is called as photon. This photon has particular energy and also momentum which proves that photon is having particle nature. This photons are electrically neutral and hence they cannot be deflected by the electric and magnetic field. Einstein showed that, the total energy of each photon received by the electron is used for two ways. Some part of its energy is used to eject the electron from the metal plate and remaining is used as the kinetic energy of the emitted photoelectron and he gave the relationship between them called as Einstein’s photoelectric equations.

The Einstein’s photoelectric equation is given as

Kmax = hv – W0

Where, h is the Planck’s constant

And v is the frequency of radiation incident

W0 is the workfuction of the metal.

Questions:

Q 1.) The momentum of each photon is given by

a) hv

b) hc/wavelength

c) hv/c

d) zero

Q 2.) The energy of photon is _____

a) depends on intensity of radiation

b) independent on intensity of radiation

c) varies linearly with intensity of radiation

d) none

Q 3.) 1eV = ____

a) 1.602*10+19J

b) 1.602*10-19 KJ

c) 1.602*10-19 J

d) 1.602*10+19 KJ

Q 4.) What is cut off or stopping potential?

Q 5.) What is work function?

Answer key:

Q 1.) c) hv/c

Q 2.) b) independent on intensity of radiation

Q 3.) c) 1.602*10-19 J

Q 4.) The minimum negative potential which is given to the collector plate in photoelectric effect leads to zero photoelectric current, such a minimum negative potential is called as cut off potential or stopping potential. Stopping potential is different for different metals.

Q 5.) The minimum amount of energy which is required by the electron to eject from the metal plate is called as work function.

Case study 2:

Light waves are nothing but the electromagnetic waves which are having dual nature. That means particle as well as wave nature. The phenomenon like interference, diffraction and polarisation of light explains the wave nature of light. While the phenomenon like photoelectric effect, Compton effect explains the particle nature of light. The physicist de Broglie proposed that every moving particle of matter is associated with wave. He gave the wavelength of that wave in terms of momentum as given below.

Wavelength = h/p = h/mv

Where, h is Planck’s constant

m is the mass of particle

And v is the speed of the particle.

And the wave associated with the matter is called as matter wave having wavelength called as de Broglie wavelength.

The most important application of photoelectric effect is the photocell. It works on the phenomenon of photoelectric effect and converts light energy into an electrical energy. The de Broglie wavelength can be measured in elementary particles like electrons, protons etc. And due to huge mass of macroscopic particles or bodies it cannot be determined in them significantly.As the wavelengths associated with macroscopic particles in our daily life is not measurable hence they doesn’t show the wave like nature. And in the microscopic particle or at atomic level the particles are having suitable wavelength which explains the wave nature associated with them. The de Broglie wavelength associated with the electron accelerated from the rest through a potential V is given by

Wavelength = 1.227/ √V nm

 Questions:

Q 1.) The de Broglie wavelength is independent of ___

a) mass of the particle

b) momentum of the particle

c) charge and nature of the particle

d) both a and b

Q 2.) Davidson and Germer, G. P. Thomson performed the electron diffraction experiment which proves the____

a) particle nature of electrons

b) dual nature of electrons

c) both a and b

d) wave nature of electrons

Q 3.) Photoelectric current depends on the___

a) intensity of incident light

b) potential difference between two electrodes

c) nature of the emitter plate material

d) all

Q 4.) If the electron is accelerated with a potential V = 54 V then what is  its de Broglie wavelength?

Q 5.) How photocell works in case of burglar alarms?

Answer key:

Q 1.) c) charge and nature of the particle

Q 2.) d) wave nature of electrons

Q 3.) d) all

Q 4.) If the electron is accelerated with potential V = 54 V then the de Broglie wavelength associated with it is given by

Wavelength = 1.227/√V = 1.227/√54 = 0.1667 nm

Q 5.) In burglar alarms, a photocell is placed or fixed at the doorway. And invisible light like ultraviolet light is falling continuously on it. If any person enters through the door it interrupts the beam of ultraviolet light falling on the photocell due to which there will be sudden change in photoelectric current and hence the bell start ringing. So one can identify or get rectified someone is came to doorsteps.

Updated: March 18, 2022 — 12:42 pm

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