The slits in a Young's double slit experiment have equal widths and the source is placed symmetrically relative to the slits. The intensity at the central fringes is I0. If one of the slits is closed, the intensity at this point will be
|
(a) I0 |
(b) I0 / 4 |
(c) I0 / 2 |
(d) 4I0 |
(b) I0 / 4
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A radioactive substance has a half life of 60 minutes. After 3 hours, the fraction of atom that have decayed would be
|
(a)12.5% |
(b) 87.5% |
(c) 8.5% |
(d) 25.1% |
A copper wire has a square cross-section, 2.0 mm on a side. It carries a current of 8 A and the density of free electrons is 8 
. The drift speed of electrons is equal to
|
(a) 0.156 × |
(b) 0.156 × |
(c) 3.12 × |
(d) 3.12 × |
A biconvex lens of glass having refractive index 1.47 is immersed in a liquid. It becomes invisible and behaves as a plane glass plate. The refractive index of the liquid is:
Monochromatic green light of wavelength 5 
illuminates a pair of slits 1 mm apart. The separation of bright lines on the interference pattern formed on a screen 2 m away is
|
(a) 0.25 mm |
(b) 0.1 mm |
(c) 1.0 mm |
(d) 0.01 mm |
The resistance of a reverse biased P-N junction diode is about
|
(a) 1 ohm |
(b) |
(c) |
(d) |
A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m. It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is
|
(a) |
(b) |
(c) |
(d) |
A thin rectangular magnet suspended freely has a period of oscillation equal to T. Now it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. If its period of oscillation is T ¢, then ratio 
is
|
(a) |
(b) |
(c) |
(d) 2 |
A 36 W galvanometer is shunted by resistance of 4W. The percentage of the total current, which passes through the galvanometer is
|
(a) 8 % |
(b) 9 % |
(c) 10 % |
(d) 91 % |
