(a) all harmonics are present in open organ pipes, while only odd harmonics
       are present in closed organ pipes
   (b) all harmonics are present in closed organ pipes, while only odd harmonics
       are present in open organ pipes
   (c) both of these
   (d) Open organ pipes are convenient to blow than closed pipes
Ans: (a)
258. Which of the following effect is also called Edison effect:
   (a) Photoelectric effect
   (b) Thermionic emission
   (c) Both of these
   (d) one of these
Ans: (b)
259. Photoelectric effect occurs only in the light of :
   (a) any wavelength
   (b) threshold wavelength
   (c) any of these
   (d) None of these
Ans: (b)
260. The famous photoelectric effect was fully explained on the basis of :
   (a) Quantum theory
   (b) Wave theory
   (c) both of these
   (d) None of these
Ans: (a)
261. Which of the following indicates the lowest temperature?
   (a) on 1° C Celcius scale
   (b) on 1K scale
   (c) on 1° F scale
   (d) on 1° R scale
Ans: (b)
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