341. In optic fiber transmission the repeater are separated through a distance of __________ km in newer system?
342. Michelson devised the formula to calculate the speed of light_______________?
A. C = 4fd
B. C = 8fd
C. C = 16fd
D. C = 5/2fd
343. A convex lens acts as a diverging lens if the_________________?
A. object is beyond C
B. if the object is with in C
C. if the object is within f
D. both B and C
344. The equation θ = 1.22 λ/D was devised by_______________?
345. Michelson calculated the speed of light using the instruments______________?
D. none of these
346. Ratio of the weight of H-atom to that of an electron is approximately______________?
347. In hydrogen spectrum which one of the following series lies in the ultraviolet region ?
A. Balmer series
B. Pfund series
C. Bracket series
D. Lymann series
348. Excited atoms return to their ground state in_______________?
349. Hydrogen atom does not emit X-rays because _________________?
A. its energy levels are too close to each other
B. its energy levels are too far apart
C. it is too small in size
D. it has a single electron
350. X-ray are________________?
A. of unknown nature
B. high energy electrons
C. high energy photons
D. radio isotopes