In a circuit, the current lags behind the voltage by a phase difference of π/2, the circuit will contain which of the following?
Only R
Only C
R and C
Only L
N identical cells, each of emf E, are connected in parallel. The emf of the combination is
NE
E
N2E
E/N
A 30 µF capacitor is charged by a constant current of 30 mA. If the capacitor is initially uncharged, how long does it take for the potential difference to reach 400 V?
0.2 s
0.4 s
0.6 s
0.8 s
The intensity of sound gets reduced by 10% on passing through a slab. The reduction in intensity on passing through two consecutive slabs would be
20 %
19 %
5 %
50 %
Four independent waves are expressed as
(i) and (iii)
(i) and (iv)
(ii) and (iv)
not possible at all
D.
not possible at all
Interference is not possible between independent waves.
Two coherent monochromatic light beams of intensities I and 4 I superimpose. The maximum and minimum possible intensities in the resulting beam are respectively
5I and I
5I and 3I
3I and I
9I and I
Ordinary light incident on a glass slab at the polarising angle suffers a deviation of 22°. The value of the angle of refraction in glass in this case is
56°
68°
34°
22°
A radioisotope has a half-life of 5 yr. The fraction of the atoms of this material that would decay in 15 yr will be
1
2/3
7/8
5/8