| Previous Year Questions of March Examinations from 2010 to 2020 |
| Chapter Name: DUAL NATURE OF RADIATION AND MATTER |
|
Light meters in photographic cameras make use of photoelectric effect. a) What is photoelectric effect? b) Which of the following photosensitive material? (a) Quartz (b) Caesium (c) Germanium (d) Silicon c) Represent graphically the variation of photoelectric current with the intensity of incident radiation. d) Red light however bright, cannot produce the emission of photoelectrons from a clean zinc surface. But even a weak ultraviolet radiation can do. Do you agree with statement? Why? |
|
To emit a free electron from a metal surface a minimum amount of energy must be supplied. a) This energy is called........... b) State three methods to supply this energy to the free electron. c) When light of frequency 7.21 x 10 14 Hz is incident on a metal surface, the maximum speed of the ejected electrons is 6 x 10 5 m/s. Calculate the threshold frequency for the metal. |
|
Read the following statements and write whether they are TRUE or FALSE. a) Matter waves are electromagnetic. b) When wavelength of incident light is decreased, the velocity of emitted photoelectrons increases. c) Alkali metals are most suitable for photoelectric emission. d) Davisson-Germen experiment proved the particle nature of electrons. |
| Given figure is the graph between frequency (υ) of the incident light and maximum kinetic energy (Ek) of emitted photoelectrons. a) Define the terms, work function and threshold frequency. b) Find the values of i. threshold frequency and ii. Work function from the graph. |
 |
|
Photon is a quanta of light a) Who introduced the concept of photon? b) Briefly explain the effect of intensity and energy of the incident radiation on the photo electric effect |
|
Albert Einstein, the great physicist proposed a clear picture to explain photoelectric effect a) Explain photo electric equation b) Name the quanta of light |
|
De Broglie proposed the wave nature of electrons suggesting matter waves Find the momentum, speed and De-Broglie wavelength of an electron with kinetic energy of 120 eV |
|
(A) Work function of a metal is the (a) energy required by an electron to get absorbed in the metal surface (b) minimum energy required by an electron to escape from the metal surface (c) energy required by an electron to be retained by a metal surface (d) maximum energy required by an electron to escape from the metal surface (B) Write Einstein’s photoelectric equation and explain the terms involved in it (C) All photoelectrons are not emitted with the same energy as the incident photons. Why? |
|
(a) What is de Broglie hypothesis? (b) Write the formula for de Broglie wavelength (c) Calculate the de Broglie wavelength associated by an electron accelerated through a potential difference of 100 volts Given mass of the electron = 9.1 x 10 -31 kg, h = 6.634 x 10 -34 JS, 1eV = 1.6 x 10 - 19 J |
|
(a) The work function a metal is 6eV.If two photons each having energy 4 eV strike with the metal surface (i) will the emission be possible? (ii) Why? (b) The waves associated with matter is called matter waves. Let λe and λp be the de Broglie wavelengths associated with electron and proton respectively. If they accelerated by same potential, then (i) λe = λp (ii) λe > λp (iii) λe = 1/λp (iv) λe < λp |
|
Momentum of a photon with wavelength λ is ………………... (i) hλ (ii) h/λ (iii) λ/h (iv) h+λ |
| Photoelectric current does not depend on energy of the radiation, but on its intensity. Explain. |
| The given graph shows the variation of KE with frequency of incident radiation for two surfaces A and B. (a) Which of the two metals has greater work function ? For which of the metals will stopping potential be more for the same frequency of incident radiation ? (b) The work function of caesium metal is 2.14 eV. When light of frequency 6 x 1014 Hz incident on the metal surface, what is the maximum KE of the photoelectrons and stopping potential ? |
 |
|
If h is Planck"s constant, the momentum of a photon of wavelength 1 A° (i) h (ii) 10-10h (iii) 1010 h (iv) 10 h |
| The schematic diagram of an experimental setup to study the wave nature of electron is shown (a) Identify the experiment. (b) Explain how this experiment verified the wave nature of electrons. |
 |
|
The work function of caesium metal is 2.14 eV. When light of frequency 6 x 1014 Hz is incident on the metal surface, photoemission of electrons occurs. (h = 6.6 x 10 –34 js) (a) Define work function. (b) Calculate the maximum kinetic energy of the emitted electrons. (c) Calculate the stopping potential. |