2019 physics mcq answers

Q.13 Which of the following property must be there in a substance so that it can be used as target in X­ray tube?
A) It must have low melting point                      C) It must have high reflecting ability
B) It must have low atomic number                    D) It must have high atomic number
Q.14 Which of the following can be used to produce population inversion for the emission of Laser?
A) Optical pumping                                            C) Optical instrument
B) Optical fibre                                                  D) Optical polarization

Q.15 X­rays from a given X­ray tube operating under specified conditions have a minimum
wavelength. The value of this minimum wavelength could be reduced by:
A) Cooling the target     C) Increasing the potential difference between the cathode and the target
B) Reducing the temperature of the filament D) Reducing the pressure in the tube
Q.16 Helium­neon lasers are used for the:
A) Precise measurement of range finding            C) Surveying for construction of tunnels
B) Optical fiber communication systems              D) Welding detached bone of body
Q.17 What is the type of characteristic X­ray photon whose energy is given by relation
‘hf = EM – EK’?
A) K – alpha                              C) K – beta
B) M – alpha                             D) M – beta