Multiple Choice QuestionsIn an electromagnetic wave in free space the root mean square value of the electric field is E rms= 6 V/m. The peak value of the magnetic field is
1.41 × 10–8 T
2.83 × 10–8 T
0.70 × 10–8 T
0.70 × 10–8 T
A long solenoid of diameter 0.1 m has 2 × 104 turns per meter. At the centre of the solenoid, a coil of 100 turns and radius 0.01 m is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to 0 A from 4 A in 0.05 s. If the resistance of the coil is 10π2 Ω, the total charge flowing through the coil during this time is
32 πμC
16 μC
32 μC
32 μC
The resistance of a wire is ‘R’ ohm. If it is melted and stretched to ‘n’ times its original length, its new resistance will be
nR
R/n
n2R
n2R
Radioactive material 'A' has a decay constant '8λ' and material 'B' has decay constant 'λ'. Initially, they have a same number of nuclei. After what time, the ratio of a number of nuclei of material 'B' to that 'A' will be 1/e?
1/λ
1/7λ
1/8λ
1/8λ
The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is
2
1
4
4
Young’s double slit experiment is first performed in air and then in a medium other than air. It is found that 8th bright fringe in the medium lies where 5th dark fringe lies in the air. The refractive index of the medium is nearly
1.25
1.59
1.69
1.69
The photoelectric threshold wavelength of silver is 3250 × 10–10 m. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536 × 10–10 m is
(Given h = 4.14 × 10–15 eVs and c = 3 × 108 ms–1)
≈ 6 × 105 ms–1
≈ 0.6 × 106 ms–1
≈61 × 103 ms–1
≈61 × 103 ms–1
A.
≈ 6 × 105 ms–1
In a common emitter transistor amplifier, the audio signal voltage across the collector is 3 V. The resistance of collector is 3 kΩ. If current gain is 100 and the base resistance is 2 kΩ, the voltage and power gain of the amplifier is
200 and 1000
15 and 200
150 and 15000
150 and 15000
Switch
