333. Which of the following rays has the highest penetrative power?
   (a) α -rays
   (b) β -rays
   (c) γ -rays
   (d) X-rays
Ans: (c)
334. A photon is
   (a) a quantum of electromagnetic radiation
   (b) light source used in photography
   (c) a photo film
   (d) sun-light
Ans: (a)
335. X-rays were discovered by
   (a) Wilhelm Roentgen
   (b) WO Coolidge
   (c) Henry Cavendish
   (d) William Watson
Ans: (a)
336. X-rays are used
   (a) in hospital in the treatment of malignant growth
   (b) to reveal hidden flaws in metal castings and welded joints
   (c) to detect alterations made in works of art
   (d) All the above
Ans: (d)
337. X-rays are
   (a) deflected by electric field
   (b) deflected by magnetic field
   (c) slightly deflected by electric field and magnetic field
   (d) not deflected by electric and magnetic fields
Ans: (d)
338. Which of the following sets of elementary particles have nearly equal