Class 12 > PYQ PHYSICS > 2014 > Set 1

2014

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Q11
For a single slit of width "a", the first minimum of the interference pattern of a monochromatic light of wavelength A occurs at an angle of 􀅗- At the same angle of t we get a maximum for two narrow slits separated by a distance "a". Explain.

Q14
State Kirchhoff's rules. Explain briefly how these rules are justified.

Q16
State the underlying principle of a cyclotron. Write briefly how this machine is used to accelerate charged particles to high energies.

Q17
An electric dipole of length 4 cm, when placed with its axis making an angle of 60 ° with a uniform electric field, experiences a torque of 4√3 Nm. Calculate the potential energy of the dipole, if it has charge ±8 nC.

Q18
A proton and a deuteron are accelerated through the same accelerating potential.
Which one of the two has
(a) greater value of de-Broglie wavelength associated with it, and
(b) less momentum ?
Give reasons to justify your answer.

Q19
(i) Monochromatic light of frequency 6.0 x 10¹⁴ Hz is produced by a laser. The power emitted is 2.0 x 10⁻³ W. Estimate the number of photons emitted per second on an average by the source.
(ii) Draw a plot showing the variation of photoelectric current versus the intensity of incident radiation on a given photosensitive surface.

Q20
A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. Upto which energy level the hydrogen atoms would be excited ?
Calculate the wavelengths of the first member of Lyman and first member of Balmer senes.

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