Tiêu đề DUAL NATURE OF RADIATION & MATTER.pdf ✅

CHAPTER 11 DUAL NATURE OF RADIATION & MATTER Exercise 1: NCERT Based Topic-wise MCQs 11.1 INTRODUCTION 1. When the speed of electrons increase, then the value of its specific char NCERT Page-387 / N-275 (a) increases (b) decreases (c) ramains unchanged (d) increases upto some velocity and then begins to decrease 2. The specific charge for cathode rays is NCERT Page-386 / N-275 (a) constant (b) variable (c) depend upon the material of the cathode (d) depend upon the nature of gas in the discharge tube 3. A strong argument for the particle nature of cathode rays is that they NCERT Page-386 / N-275 (a) produce fluoroscence (b) travel through vacuum (c) get deflected by electric and magnetic fields (d) cast shadow 4. In an electron gun the control grid is given a negative potential relative to cathode in order to (a) decelerate electrons NCERT Page-386 / N-275 (b) repel electrons and thus to control the number of electrons passing through it (c) to select electrons of same velocity and to converge them along the axis. (d) to decrease the kinetic energy of electrons 5. Cathode rays and canal rays produced in a certain discharge tube are deflected in the same direction if (a) a magnetic field is applied normally NCERT Page-386 / N-275 (b) an electric field is applied normally (c) an electrin field is applied tangentially (d) a magnetic field is applied tangentially 6. Cathode rays are made to pass between the poles of a magnet perpendicular to axis, the effect of the magnetic field is NCERT Page-386 / N-275 (a) to increase the velocity of rays (b) to deflect them towards the north pole (c) to deflect them towards the south pole (d) to deflect them upwards above the plane of paper
11.2 ELECTRON EMISSION 7. In which of the following, emission of electrons does not take place? NCERT Page-387 / N-275, 276 (a) Thermionic emission (b) X-rays emission (c) Photoelectric emission (d) Secondary emission 11.3 PHOTOELECTRIC EFFECT 8. Photoelectric effect is the phenomenon in which NCERT Page-388 / N-276 (a) photons come out of a metal when it is hit by a beam of electrons. (b) photons come out of the nucleus of an atom under the action of an electric field. (c) electrons come out of a metal with a constant velocity (d) which depends on the frequency and intensity of incident light wave. 9. Photoelectric emmision occurs only when the incident light has more than a certain minimum (a) power NCERT Page-388 / N-276 (b) wavelength (c) intensity (d) frequency 10. The frequency and work function of an incident photon are v and φ0. If v0 is the threshold frequency then necessary condition for the emission of photoelectron is NCERT Page-388 / N-276 (a) v < v0 (b) v = v0 2 (c) v ≥ v0 (d) None of these 11.4 EXPERIMENTAL STUDY OF PHOTOELECTRIC EFFECT 11. With reference to the observations in photo-electric effect, identify the correct statements from below: A. The square of maximum velocity of photoelectrons varies linearly with frequency of incident light. B. The value of saturation current increases on moving the source of light away from the metal surface. C. The maximum kinetic energy of photo-electrons decreases on decreasing the power of LED (light emitting diode) source of light. D. The immediate emission of photo-electrons out of metal surface can not be explained by particle nature of light/electromagnetic waves. E. Existence of threshold wavelength can not be explained by wave nature of light/electromagnetic waves. Choose the correct answer from the options given below: NCERT/ Page-391 / N-278 (a) A and B only (c) C and E only (b) A and E only (d) D and E only 12. The stopping potential is directly related to NCERT Page-391 / N-278 (a) the work function of the metal (b) intensity of incident radiation (c) the saturation current for the given frequency (d) the kinetic energy gained by the photoelectrons 13 . When light is incident on a metal surface the maximum kinetic energy of emitted electrons
(a) vary with intensity of light NCERT Page-391 / N-278 (b) vary with frequency of light (c) vary with speed of light (d) vary irregularly 14. Light of a particular frequency v is incident on a metal surface. When the intensity of incident radiation is increased, the photoelectric current NCERT Page-392 / N-279 (a) decreases (b) increases (c) remains unchanged (d) sometimes increases and sometimes decreases 15.The kinetic energy of emitted electron is E when the light incident on the metal has wavelength λ. To double the kinetic energy, the incident light must have wavelength : NCERT Page-392 / N-279 (a) hc Eλ−hc (b) hcλ Eλ+hc (c) hλ Eλ+hc (d) hcλ Eλ−hc 16. For a given photosensitive material and frequency ( > threshold frequency) of incident radiation, the photoelectric current varies with the intensity of incident light as NCERT Page-390 / N-277 (a) (b) (c) (d) 17. The maximum kinetic energy (Emax ) of photoelectrons emitted in a photoelectric cell varies with frequency (v) as shown in the graph. The slope of the graph is equal to NCERT Page-392 / N-279 (a) charge of the electron (b) e m of the electron (c) work function of the emitter (d) Plank's constant 18. In a photoelectric experiment, anode potential (v) is plotted against plate current (I) NCERT Page-391 / N-278 (a) A and B will have different intensities while B and C will have different frequencies (b) B and C will have different intensities while A aîdC will have different frequencies
(c) A and B will have different intensities while A and C2−5 will have equal frequencies (d) A and B will have equal intensities while B and C will have different frequencies 11.5 PHOTOELECTRIC EFFECT AND WAVE THEORY 19. The Electromagnetic theory of failed to explain NCERT Page-393 / N-281 (a)photoelectric effect (b)polarization (c) diffraction (d) interference 11.6 EINSTEIN’S PHOTOELECTRIC EQUATION:ENERGY QUANTUM OF RADIATION 20. The electric field at the point associated with a light wave is given by E = 200[sin (6 × 1015)t + sin (9 × 1015)t]Vm−1 Given : h = 4.14 × 10−15eVs If this light falls on a metal surface having a work function of 2.50eV, the maximum kinetic energy of the photoelectrons will be : NCERT Page-394 / N-281 (a) 1.90eV (b) 3.27eV (c) 3.60eV (d) 3.42eV 21. The work-function of a metal is NCERT Page-394 / N-281 (a) the minimum current required to take out electron from the metal surface (b) the maximum frequency required to take out electron from the metal surface (c) the minimum amount of energy required to take out the electron from the metal surface (d) None of these 22. The work function of a substance is 4.0eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately NCERT Page-394/ N-281 (a) 310nm (b) 400nm (c) 540nm (d) 220nm 23. A monochromatic source of light operating at 200W emits 4 × 1020 photons per second. Find the wavelength of light. NCERT Page-394 / N-281 (a) 400nm (b) 200nm (c) 4 × 10−10Å (d) None of these 24. Sodium and copper have work functions 2.3eV and 4.5eV respectively. Then the ratio of the wavelengths is nearest to NCERT Page-394 / N-281 (d) 1: 4 (a) 1: 2 (b) 4: 1 (c) 2: 1 25. The work functions of Silver and Sodium are 4.6 and 2.3eV, respectively. The ratio of the slope of the stopping potential versus frequency plot for Silver to that of Sodium is NCERT Page-394 / N-281 (a) 1 (b) 2