A train is moving on a straight track with speed 20 ms-1 .It is blowing its whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is (speed of sound = 320 ms-1 ) close to :
6%
12%
18%
18%
B.
12%
Apparent frequency heard by the person before crossing the train.
Similarly, apparent frequency heard, after crossing the trains
A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.
10.62 MHz
10.62 kHz
5.31 mHz
5.31 mHz
B.
10.62 kHz
The frequency is given as
μ =0.6
R = 100 k = 100 x1000 Ω
c = 250 pico farad = 250 x 10-12 F
So,
Arrange the following electromagnetic radiations per quantum in the order of increasing energy:
A: Blue light
B: Yellow light
C: X-ray
D: Radiowave
D, B, A, C
A, B, D, C
C, A, B, D
C, A, B, D
A.
D, B, A, C
As, we know energy liberated, E = hc/λ
i.e 
So, lesser the wavelength greater will be energy liberated by electromagnetic radiations per quantum.
As, order of wavelength is given by
X- rays, VIBGYOR, Radio waves
therefore, the order of electromagnetic radiations per quantum.
D<B<A<C
Choose the correct statement:
In amplitude modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
In amplitude modulation, the frequency of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
In frequency modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
In frequency modulation, the amplitude of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
B.
In amplitude modulation, the frequency of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
As, we know, an amplitude modulated wave, the bandwidth is twice the frequency of modulating the signal. Therefore, amplitude modulation (AM), the frequency of the high-frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. The frequencies of the resultant signal is/are:
2005 kHz, and 1995 kHz
2005 kHz, 2000 kHz and 1995 kHz
2000 kHz and 1995 kHz
2000 kHz and 1995 kHz
C.
2000 kHz and 1995 kHz
Frequency associated with AM are
fc - fm, f, fc + fm
according to the question
fc = 2 MHz = 2000 kHz
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