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31. The specific gravity of oxygen and nitrogen are in the ratio 16:14. The temperature at which the velocity of sound will be the same as that of nitrogen at       

       288 K is

      a. 385 K    b. 345 K          c. 321 K          d. 329 K

 

32. For certain radioactive material, decay involves two processes with the half life periods 60min and 30 min repectively. The effective value of half life

      period would be

      a. 20 min    b. 45 min          c. 15 min          d. 90 min

 

33. A cylinder contains acetylene at 300 K under a pressure of 4.05 MPa. What will be the pressure in the cylinder after half the mass of  gas has been used up

      if the temperature fallen thereby to 285K?

       a. 1.92 3 10⁶ Pa              b. 2.205 3 10⁶Pa        c. 1.025 3 10⁶ Pa       d. 1.92 3 10⁵Pa

 

34. Which of the following statements is correct

1. When frequency of the incident photons is doubled, stopping potential also gets doubled
2. Two photons having equal wavelengths have equal linear momenta
3. When a point source emitting monochromatic radiation is moved closer to the metal surface in a photoelectric experiment, stopping potential

Decreases

4. None of these

 

35. The K_a line from Mo(Z=42) has a wavelength 0.7078 Å. What will be the wavelength of K_a line for an element whose atomic number is 30?

      a. 1.414 Å              b. 2.12 Å         c. 2.8 Å            d. 3.5390 Å