CBSE Guess > Papers > Important Questions > Class XII > 2011 > Physics > Physics By Mr. Ajay Sharma

CBSE CLASS XII

Dual Nature Of Matter and Radiation

(Q.1) What is the momentum of an electron moving with speed of 2x10¹⁰ m/s? ( 1 mark )

(a) 4.92x10^-24 kg m/s
(b) 1.82x10²⁰ kg m/s
(c) 3.2x10²⁵ kg m/s
(d) 3.2 10^-9 kg m/s

(Q.2) Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material, photoelectric current is emitted. If the frequency of light is halved and intensity is doubled, the photoelectric current becomes: ( 1 mark )

(a) 4 times the original current
(b) 2 times the original current
(c) Half the original current
(d) Zero times the original current

(Q.3) What do you mean by work function? ( 1 mark )

(Q.4) What is the rest mass of photon? ( 1 mark )

(Q.5) What is the effect on the velocity of the emitted photoelectrons if the wavelength of the incident light is decreased? (1mark )

(Q.6) On what factor the retarding potential of photo cell depends? ( 1 mark )

(Q.7) With what purpose was famous Davisson-Germer experiment with electrons performed? (H) ( 1 mark )

(Q.8) Do non-metals show photoelectric effect? ( 1 mark )

(Q.9) Light from the bulb falls on the wooden table, but no photoelectrons are emitted. Why? ( 1 mark )

(Q.10) How will the photoelectric current change on decreasing the wavelength of incident radiation for a given photo-sensitive material? (H) ( 1 mark )

(Q.11) It is harder to remove free electron from copper than from sodium. Which has higher work function? ( 1 mark )

(Q.12) What determines the maximum velocity of the photoelectrons? ( 1 mark )

(Q.13) The graph between, which of the following two factors for photoelectric effect, is a straight line? ( 1 mark )

(a) Intensity of radiation and photoelectric current
(b) Potential of anode and photoelectric current
(c) Threshold frequency and velocity of photoelectrons
(d) Intensity of radiations and stopping potential

(Q.14) A particle which has zero rest mass and non-zero energy and momentum must travel with a speed. ( 1 mark )

(a) Equal to c, the speed of light in vacuum
(b) Greater than c
(c) Less than c
(d) Tending to infinity

(Q.15) The maximum energy of electrons released in a photocell is independent of: ( 1 mark )

(a) The frequency of the incident light.
(b) The intensity of the incident light.
(c) The nature of the cathode.
(d) All are true

(Q.16) A metal surface is illuminated by the photons of energy 5 eV and 2.5 eV respectively. The ratio of their wavelengths is: ( 1 mark )

(a) 1 : 3
(b) 1 : 4
(c) 2 : 1
(d) 1 : 2

(Q.17) Which of the following is correct? ( 1 mark )

(a) The current in a photocell increases with increasing frequency.
(b) The photocurrent is proportional to the applied voltage.
(c) The stopping potential increases with the intensity of light.
(d) The photocurrent increases with the intensity of light.

(Q.18) Which one among the following shows particle nature of light ? ( 1 mark )

(a) Photoelectric effect
(b) Interference
(c) Refraction
(d) Polarisation

(Q.19) For the Davison Germer experiment if the angle of diffraction be 52°, then what is the glancing angle? (H) ( 1 mark )

(a) 26°
(b) 64°
(c) 52°
(d) 104°

(Q.20) The correct curve between the stopping potential (Vs) and intensity of incident light (I) is: (H) ( 1 mark )

(a)

(b)

(c)

(d)

 

(Q.21) In photoelectric effect the slope of straight line graph between stopping potential (V₀) and frequency of incident light(V)gives: ( 1 mark )

(a) Planck's constant.
(b) Work function of emitter.
(c) Charge on electron.
(d) Ratio of Planck's constant to charge on electron.

(Q.22) Photoelectric effect is the phenomenon in which: ( 1 mark )

(a) Photons come out of a metal when it is hit by the 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 which depends upon the frequency and intensity of the incident light wave.
(d) Electrons come out of metal with different velocities not greater than a certain value which depends only on the frequency of the incident light wave and not on its intensity

(Q.23) In photoelectric effect, the photocurrent: ( 1 mark )

(a) Depends both on intensity and frequency of the incident light.
(b)\Does not depend on the frequency of photon but depends only on intensity of incident light.
(c) Decreases with increase of frequency of incident photon.
(d) Increases with increase of frequency of incident photon.

(Q.24) A metal surface ejects electrons when hit by green light but none when hit by yellow light. The electrons will be ejected when the surface is hit by: (H) ( 1 mark )

(a) Blue light
(b) Heat rays
(c) Infra-red light
(d) Red light

(Q.25) Monochromatic light of frequency 2x10¹⁵ Hz is produced by a laser. What is the energy of a photon in the light beam? ( 1 mark )

(a) 1.32x10-^-18
(b) 1.2x10-^-12
(c) 2.4x10^-45
(d) 3.6x10^-20

(Q.26) Which one of the followingwill deflect in electric field ? ( 1 mark )

(a) - rays
(b) X-rays
(c) UV-rays
(d) Cathode ray

(Q.27) what is the frequency associated with a photon of energy 1.1x10^-20 J. (h=6.6x10^-34 Js) (1mark )

(a) 1.66x10¹³ Hz
(b) 2.4x10⁸ Hz
(c) 2.3x10⁸ Hz
(d) 1.4x10⁶ H

(Q.28) Which one among the following shows particle nature of light? ( 1 mark )

(a) Interference
(b) Refraction
(c) Photoelectric effect
(d) Polarisation

(Q.29) A proton and particle are accelerated through the same potential difference. The ratio of their de-Broglie wavelength will be: (H) ( 1 mark )

(a) 1 : 1
(b) 1 : 2
(c) 2 : 1
(d) 2 ѵ 2 : 1

(Q.30) If E and p are the energy and the momentum of a photon respectively then on increasing the wavelength of photon: ( 1 mark )

(a) p and E both will decrease
(b) p and E both will increase
(c) p will increase and E will decrease
(d) p will decrease and E will increase<

(Q.31) Dual nature of radiation is shown by: ( 1 mark )

(a) Diffraction and reflection
(b) Refraction and diffraction
(c) Photoelectric effect alone
(d) Photoelectric effect and diffraction

(Q.32) If a photon and an electron have same de-Broglie wavelength, then: ( 1 mark )

(a) Both have same kinetic energies.
(b) Proton has more K.E. than electron.
(c) Electron has more K.E. than proton.
(d) Both have same velocity.

(Q.33) The wavelength of a 1 keV photon is 1.24 × 10^–9 m. What is the frequency of 1 MeV photon? (H) ( 1 mark )

(a) 2.4 × 10¹⁵ Hz
(b) 2.4 × 10²⁰ Hz
(c) 1.24 × 10¹⁵ Hz
(d) 1.24 × 10²⁰ Hz

(Q.34) Which one of the following statements about photon is not correct? ( 1 mark )

(a) Photons exert no pressure
(b) Photons energy is hv
(c) Momentum of photon is hv / c
(d) Photon rest mass is zero

(Q.35) The photoelectric effect is a phenomenon which can be used to convert: ( 1 mark )

(a) Electric energy into mechanical energy.
(b) Light energy into electric energy.
(c) Photon into electron
(d) Light energy into mechanical energy.

(Q.36) What is E in the Einstein's photoelectric equation :E = hv - w₀ where is the frequency of incident radiations and w₀ is the work function? (H) ( 1 mark )

(a) Kinetic energy of every photoelectron
(b) Mean kinetic energy of photoelectrons
(c) Minimum kinetic energy of photoelectrons
(d) Maximum kinetic energy of photoelectrons

(Q.37) Cathode rays , enter a magnetic field normal to the lines of force , then their path in the magnetic field is ( 1 mark )

(a) straight line
(b) ellipse
(c) circle
(d) parabola

(Q.38) Proton and alpha particle have the same de-Broglie wavelength. What is the same for both of them ? ( 1 mark )

(a) Time period
(b) Energy
(c) Frequency
(d) Momentum

(Q.39) The slope of frequency of incident light and stopping potential for a given surface will be ( 1 mark )

(a) h
(b) h/e
(c) eh
(d) e

(Q.40) The de Broglie wavelength of an atom of mass m of a diatomic gas at temperature T will be: (H) ( 1 mark )

(Q.41) An electron α particle, and a proton have the same kinetic energy. Which of these particles has the shortest de-Broglie wavelength? ( 2 Marks )

(Q.42) What will be the wavelength of an electron of energy 1000 eV? ( 2 Marks )

(Q.43) Define the terms: threshold frequency and stopping potential for photoelectric effect ? ( 2 Marks )

(Q.44) Calculate the frequency associated with the photon of energy 3.3 x 10^-20J. ( 2 Marks )

(Q.45) The photoelectric cut-off voltage in a certain experiment is 2 V. What is the maximum kinetic energy of photoelectrons emitted? (H) ( 2 Marks )

(Q.46) On what factors does the energy carried by a photon of light depend? ( 2 Marks )

(Q.47) For photoelectric effect in a metal, the figure shows the plot of cut-off voltage versus frequency of incident radiation. Calculate:

(a) The threshold frequency.
(b) The work function for metal. (H)

(Q.48) A radio transmitter operates at a frequency of 880 kHz and a power of 10 kW. Find the number of photons emitted per second. ( 3 Marks )

(Q.49) An electron and proton have the same kinetic energy. Which of the two has greater wavelength? Justify your answer. What is the momentum of a photon of frequency ט . (3 Marks)

(Q.50) Explain the functioning of photocell. Give its uses. ( 3 Marks )

(Q.51) State the laws of photoelectric emission. ( 3 Marks )

(Q.52) Show that the de Broglie’s wavelength of electrons accelerated through potential V volts can be expressed as, (H)

 

Submitted By Mr. Ajay Sharma
Email Id : [email protected]