(b) holes
   (c) both of these
   (d) none of these
Ans: (b)
272. In n-type of semiconductor the current mainly flows due to:
   (a) electrons
   (b) holes
   (c) both of these
   (d) none of these
Ans: (a)
273. A diffraction pattern is obtained using a beam of red light. Which one
   among the following will be the outcome if the red light is replaced by blue
   light? [CDS 2010]
   (a) Bands disappear
   (b) Diffraction pattern becomes broader and further apart
   (c) Diffraction pattern becomes narrower and crowded .together
   (d) No change
Ans: (b)
274. The transistor acts like:
   (a) an amplifier
   (b) an oscillator
   (c) both of these
   (d) None of these
Ans: (c)
275. Which one of the following statements is true? [CDS 2010]
   (a) Temperatures differing by 25°on the Fahrenheit (F) scale must differ by
       45°on the Celsius (C) scale
   (b) 0° F corresponds to -32°C
   (c) Temperatures which differ by 10° on the Celsius scale must differ by
       18°on the Fahrenheit scale
   (d) Water at 90°Cis warmer than water at 202° F
Ans: (c)
                                        199